diff --git a/.travis.yml b/.travis.yml
index 9d14a9a..af90a1b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,7 +1,7 @@
 language: dart
 sudo: required
 dart:
-  - stable
+  - beta
 addons:
   postgresql: "9.6"
 services:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index ca20fdc..08e1fa0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## 2.3.0
+
+- Migrate to null safety
+
 ## 2.2.0
 
 - Supporting Unix socket connections. (Thanks to [grillbiff](https://github.com/grillbiff),
diff --git a/lib/src/binary_codec.dart b/lib/src/binary_codec.dart
index 89c75ce..aa4c75b 100644
--- a/lib/src/binary_codec.dart
+++ b/lib/src/binary_codec.dart
@@ -28,13 +28,13 @@ final _hex = <String>[
   'f',
 ];
 
-class PostgresBinaryEncoder extends Converter<dynamic, Uint8List> {
+class PostgresBinaryEncoder extends Converter<dynamic, Uint8List?> {
   final PostgreSQLDataType _dataType;
 
   const PostgresBinaryEncoder(this._dataType);
 
   @override
-  Uint8List convert(dynamic value) {
+  Uint8List? convert(dynamic value) {
     if (value == null) {
       return null;
     }
@@ -169,7 +169,7 @@ class PostgresBinaryEncoder extends Converter<dynamic, Uint8List> {
                 'Invalid type for parameter value. Expected: String Got: ${value.runtimeType}');
           }
 
-          final hexBytes = (value as String)
+          final hexBytes = value
               .toLowerCase()
               .codeUnits
               .where((c) => c != _dashUnit)
@@ -199,9 +199,9 @@ class PostgresBinaryEncoder extends Converter<dynamic, Uint8List> {
           }
           return outBuffer;
         }
+      default:
+        throw PostgreSQLException('Unsupported datatype');
     }
-
-    throw PostgreSQLException('Unsupported datatype');
   }
 }
 
@@ -211,13 +211,13 @@ class PostgresBinaryDecoder extends Converter<Uint8List, dynamic> {
   final int typeCode;
 
   @override
-  dynamic convert(Uint8List value) {
-    final dataType = typeMap[typeCode];
-
+  dynamic convert(Uint8List? value) {
     if (value == null) {
       return null;
     }
 
+    final dataType = typeMap[typeCode];
+
     final buffer =
         ByteData.view(value.buffer, value.offsetInBytes, value.lengthInBytes);
 
@@ -277,16 +277,18 @@ class PostgresBinaryDecoder extends Converter<Uint8List, dynamic> {
 
           return buf.toString();
         }
-    }
-
-    // We'll try and decode this as a utf8 string and return that
-    // for many internal types, this is valid. If it fails,
-    // we just return the bytes and let the caller figure out what to
-    // do with it.
-    try {
-      return utf8.decode(value);
-    } catch (_) {
-      return value;
+      default:
+        {
+          // We'll try and decode this as a utf8 string and return that
+          // for many internal types, this is valid. If it fails,
+          // we just return the bytes and let the caller figure out what to
+          // do with it.
+          try {
+            return utf8.decode(value);
+          } catch (_) {
+            return value;
+          }
+        }
     }
   }
 
diff --git a/lib/src/client_messages.dart b/lib/src/client_messages.dart
index e072c07..c085657 100644
--- a/lib/src/client_messages.dart
+++ b/lib/src/client_messages.dart
@@ -42,11 +42,11 @@ void _applyStringToBuffer(UTF8BackedString string, ByteDataWriter buffer) {
 }
 
 class StartupMessage extends ClientMessage {
-  final UTF8BackedString _username;
+  final UTF8BackedString? _username;
   final UTF8BackedString _databaseName;
   final UTF8BackedString _timeZone;
 
-  StartupMessage(String databaseName, String timeZone, {String username})
+  StartupMessage(String databaseName, String timeZone, {String? username})
       : _databaseName = UTF8BackedString(databaseName),
         _timeZone = UTF8BackedString(timeZone),
         _username = username == null ? null : UTF8BackedString(username);
@@ -58,7 +58,7 @@ class StartupMessage extends ClientMessage {
 
     if (_username != null) {
       fixedLength += 5;
-      variableLength += _username.utf8Length + 1;
+      variableLength += _username!.utf8Length + 1;
     }
 
     buffer.writeInt32(fixedLength + variableLength);
@@ -66,7 +66,7 @@ class StartupMessage extends ClientMessage {
 
     if (_username != null) {
       buffer.write(UTF8ByteConstants.user);
-      _applyStringToBuffer(_username, buffer);
+      _applyStringToBuffer(_username!, buffer);
     }
 
     buffer.write(UTF8ByteConstants.database);
@@ -83,7 +83,7 @@ class StartupMessage extends ClientMessage {
 }
 
 class AuthMD5Message extends ClientMessage {
-  UTF8BackedString _hashedAuthString;
+  UTF8BackedString? _hashedAuthString;
 
   AuthMD5Message(String username, String password, List<int> saltBytes) {
     final passwordHash = md5.convert('$password$username'.codeUnits).toString();
@@ -96,9 +96,9 @@ class AuthMD5Message extends ClientMessage {
   @override
   void applyToBuffer(ByteDataWriter buffer) {
     buffer.writeUint8(ClientMessage.PasswordIdentifier);
-    final length = 5 + _hashedAuthString.utf8Length;
+    final length = 5 + _hashedAuthString!.utf8Length;
     buffer.writeUint32(length);
-    _applyStringToBuffer(_hashedAuthString, buffer);
+    _applyStringToBuffer(_hashedAuthString!, buffer);
   }
 }
 
@@ -157,14 +157,14 @@ class BindMessage extends ClientMessage {
   final List<ParameterValue> _parameters;
   final UTF8BackedString _statementName;
   final int _typeSpecCount;
-  int _cachedLength;
+  int _cachedLength = -1;
 
   BindMessage(this._parameters, {String statementName = ''})
       : _typeSpecCount = _parameters.where((p) => p.isBinary).length,
         _statementName = UTF8BackedString(statementName);
 
   int get length {
-    if (_cachedLength == null) {
+    if (_cachedLength == -1) {
       var inputParameterElementCount = _parameters.length;
       if (_typeSpecCount == _parameters.length || _typeSpecCount == 0) {
         inputParameterElementCount = 1;
@@ -221,7 +221,7 @@ class BindMessage extends ClientMessage {
         buffer.writeInt32(-1);
       } else {
         buffer.writeInt32(p.length);
-        buffer.write(p.bytes);
+        buffer.write(p.bytes!);
       }
     });
 
diff --git a/lib/src/connection.dart b/lib/src/connection.dart
index ba3455e..09c8250 100644
--- a/lib/src/connection.dart
+++ b/lib/src/connection.dart
@@ -67,10 +67,10 @@ class PostgreSQLConnection extends Object
   final String databaseName;
 
   /// Username for authenticating this connection.
-  final String username;
+  final String? username;
 
   /// Password for authenticating this connection.
-  final String password;
+  final String? password;
 
   /// Whether or not this connection should connect securely.
   final bool useSSL;
@@ -113,18 +113,18 @@ class PostgreSQLConnection extends Object
 
   final _cache = QueryCache();
   final _oidCache = _OidCache();
-  Socket _socket;
+  Socket? _socket;
   MessageFramer _framer = MessageFramer();
-  int _processID;
+  late int _processID;
   // ignore: unused_field
-  int _secretKey;
-  List<int> _salt;
+  late int _secretKey;
+  late List<int> _salt;
 
   bool _hasConnectedPreviously = false;
-  _PostgreSQLConnectionState _connectionState;
+  late _PostgreSQLConnectionState _connectionState;
 
   @override
-  PostgreSQLExecutionContext get _transaction => null;
+  PostgreSQLExecutionContext get _transaction => this;
 
   @override
   PostgreSQLConnection get _connection => this;
@@ -156,11 +156,12 @@ class PostgreSQLConnection extends Object
 
       _framer = MessageFramer();
       if (useSSL) {
-        _socket = await _upgradeSocketToSSL(_socket, timeout: timeoutInSeconds);
+        _socket =
+            await _upgradeSocketToSSL(_socket!, timeout: timeoutInSeconds);
       }
 
       final connectionComplete = Completer();
-      _socket.listen(_readData, onError: _close, onDone: _close);
+      _socket!.listen(_readData, onError: _close, onDone: _close);
 
       _transitionToState(
           _PostgreSQLConnectionStateSocketConnected(connectionComplete));
@@ -214,7 +215,7 @@ class PostgreSQLConnection extends Object
   /// default query timeout will be used.
   Future transaction(
     Future Function(PostgreSQLExecutionContext connection) queryBlock, {
-    int commitTimeoutInSeconds,
+    int? commitTimeoutInSeconds,
   }) async {
     if (isClosed) {
       throw PostgreSQLException(
@@ -229,7 +230,7 @@ class PostgreSQLConnection extends Object
   }
 
   @override
-  void cancelTransaction({String reason}) {
+  void cancelTransaction({String? reason}) {
     // Default is no-op
   }
 
@@ -249,13 +250,15 @@ class PostgreSQLConnection extends Object
     _connectionState.connection = this;
   }
 
-  Future _close([dynamic error, StackTrace trace]) async {
+  Future _close([dynamic error, StackTrace? trace]) async {
     _connectionState = _PostgreSQLConnectionStateClosed();
 
-    await _socket?.close();
-    await _notifications?.close();
+    if (_socket != null) {
+      await _socket!.close();
+    }
+    await _notifications.close();
 
-    _queue?.cancel(error, trace);
+    _queue.cancel(error, trace);
   }
 
   void _readData(List<int> bytes) {
@@ -355,16 +358,16 @@ class _OidCache {
 
   Future<List<FieldDescription>> _resolveTableNames(
       _PostgreSQLExecutionContextMixin c,
-      List<FieldDescription> columns) async {
-    if (columns == null) return null;
+      List<FieldDescription?>? columns) async {
+    if (columns == null) return [];
     //todo (joeconwaystk): If this was a cached query, resolving is table oids is unnecessary.
     // It's not a significant impact here, but an area for optimization. This includes
     // assigning resolvedTableName
     final unresolvedTableOIDs = columns
-        .map((f) => f.tableID)
+        .where((f) => f != null)
+        .map((f) => f!.tableID)
         .toSet()
-        .where((oid) =>
-            oid != null && oid > 0 && !_tableOIDNameMap.containsKey(oid))
+        .where((oid) => oid > 0 && !_tableOIDNameMap.containsKey(oid))
         .toList()
           ..sort();
 
@@ -373,7 +376,7 @@ class _OidCache {
     }
 
     return columns
-        .map((c) => c.change(tableName: _tableOIDNameMap[c.tableID]))
+        .map((c) => c!.change(tableName: _tableOIDNameMap[c.tableID]))
         .toList();
   }
 
@@ -387,6 +390,10 @@ class _OidCache {
       resolveOids: false,
     );
 
+    if (orderedTableNames == null) {
+      return;
+    }
+
     final iterator = oids.iterator;
     orderedTableNames.forEach((tableName) {
       iterator.moveNext();
@@ -409,11 +416,11 @@ abstract class _PostgreSQLExecutionContextMixin
   int get queueSize => _queue.length;
 
   @override
-  Future<PostgreSQLResult> query(
+  Future<PostgreSQLResult?> query(
     String fmtString, {
-    Map<String, dynamic> substitutionValues,
-    bool allowReuse,
-    int timeoutInSeconds,
+    Map<String, dynamic>? substitutionValues,
+    bool allowReuse = true,
+    int? timeoutInSeconds,
   }) =>
       _query(
         fmtString,
@@ -422,16 +429,14 @@ abstract class _PostgreSQLExecutionContextMixin
         timeoutInSeconds: timeoutInSeconds,
       );
 
-  Future<PostgreSQLResult> _query(
+  Future<PostgreSQLResult?> _query(
     String fmtString, {
-    Map<String, dynamic> substitutionValues,
-    bool allowReuse,
-    int timeoutInSeconds,
-    bool resolveOids,
+    Map<String, dynamic>? substitutionValues,
+    required bool allowReuse,
+    int? timeoutInSeconds,
+    bool resolveOids = true,
   }) async {
-    allowReuse ??= true;
     timeoutInSeconds ??= _connection.queryTimeoutInSeconds;
-    resolveOids ??= true;
 
     if (_connection.isClosed) {
       throw PostgreSQLException(
@@ -451,34 +456,41 @@ abstract class _PostgreSQLExecutionContextMixin
       columnDescriptions = await _connection._oidCache
           ._resolveTableNames(this, columnDescriptions);
     }
-    final metaData = _PostgreSQLResultMetaData(columnDescriptions);
-
-    return _PostgreSQLResult(
-        queryResult.affectedRowCount,
-        metaData,
-        queryResult.value
-            .map((columns) => _PostgreSQLResultRow(metaData, columns))
-            .toList());
+    final metaData = _PostgreSQLResultMetaData(columnDescriptions!);
+
+    return queryResult != null
+        ? _PostgreSQLResult(
+            queryResult.affectedRowCount,
+            metaData,
+            queryResult.value!
+                .map((columns) => _PostgreSQLResultRow(metaData, columns))
+                .toList())
+        : null;
   }
 
   @override
-  Future<List<Map<String, Map<String, dynamic>>>> mappedResultsQuery(
+  Future<List<Map<String?, Map<String, dynamic>>>> mappedResultsQuery(
       String fmtString,
-      {Map<String, dynamic> substitutionValues,
-      bool allowReuse,
-      int timeoutInSeconds}) async {
+      {Map<String, dynamic> substitutionValues = const {},
+      bool allowReuse = false,
+      int? timeoutInSeconds}) async {
     final rs = await query(
       fmtString,
       substitutionValues: substitutionValues,
       allowReuse: allowReuse,
       timeoutInSeconds: timeoutInSeconds,
     );
+
+    if (rs == null) {
+      return Future.value();
+    }
     return rs.map((row) => row.toTableColumnMap()).toList();
   }
 
   @override
-  Future<int> execute(String fmtString,
-      {Map<String, dynamic> substitutionValues, int timeoutInSeconds}) async {
+  Future<int?> execute(String fmtString,
+      {Map<String, dynamic> substitutionValues = const {},
+      int? timeoutInSeconds}) async {
     timeoutInSeconds ??= _connection.queryTimeoutInSeconds;
     if (_connection.isClosed) {
       throw PostgreSQLException(
@@ -490,13 +502,13 @@ abstract class _PostgreSQLExecutionContextMixin
         onlyReturnAffectedRowCount: true);
 
     final result = await _enqueue(query, timeoutInSeconds: timeoutInSeconds);
-    return result.affectedRowCount;
+    return result != null ? result.affectedRowCount : null;
   }
 
   @override
   void cancelTransaction({String reason});
 
-  Future<QueryResult<T>> _enqueue<T>(Query<T> query,
+  Future<QueryResult<T>?> _enqueue<T>(Query<T> query,
       {int timeoutInSeconds = 30}) async {
     if (_queue.add(query)) {
       _connection._transitionToState(_connection._connectionState.awake());
@@ -521,18 +533,19 @@ abstract class _PostgreSQLExecutionContextMixin
     }
   }
 
-  Future _onQueryError(Query query, dynamic error, [StackTrace trace]) async {}
+  Future _onQueryError(Query query, dynamic error, [StackTrace? trace]) async {}
 }
 
 class _PostgreSQLResultMetaData {
-  final List<ColumnDescription> columnDescriptions;
-  List<String> _tableNames;
+  final List<ColumnDescription?> columnDescriptions;
+  late List<String?> _tableNames;
 
-  _PostgreSQLResultMetaData(this.columnDescriptions);
+  _PostgreSQLResultMetaData(this.columnDescriptions) {
+    _tableNames =
+        columnDescriptions.map((column) => column!.tableName).toSet().toList();
+  }
 
-  List<String> get tableNames {
-    _tableNames ??=
-        columnDescriptions.map((column) => column.tableName).toSet().toList();
+  List<String?> get tableNames {
     return _tableNames;
   }
 }
@@ -548,7 +561,7 @@ class _PostgreSQLResult extends UnmodifiableListView<PostgreSQLResultRow>
       : super(rows);
 
   @override
-  List<ColumnDescription> get columnDescriptions =>
+  List<ColumnDescription?> get columnDescriptions =>
       _metaData.columnDescriptions;
 }
 
@@ -559,18 +572,18 @@ class _PostgreSQLResultRow extends UnmodifiableListView
   _PostgreSQLResultRow(this._metaData, List columns) : super(columns);
 
   @override
-  List<ColumnDescription> get columnDescriptions =>
+  List<ColumnDescription?> get columnDescriptions =>
       _metaData.columnDescriptions;
 
   @override
-  Map<String, Map<String, dynamic>> toTableColumnMap() {
-    final rowMap = <String, Map<String, dynamic>>{};
+  Map<String?, Map<String, dynamic>> toTableColumnMap() {
+    final rowMap = <String?, Map<String, dynamic>>{};
     _metaData.tableNames.forEach((tableName) {
       rowMap[tableName] = <String, dynamic>{};
     });
     for (var i = 0; i < _metaData.columnDescriptions.length; i++) {
       final col = _metaData.columnDescriptions[i];
-      rowMap[col.tableName][col.columnName] = this[i];
+      rowMap[col!.tableName]![col.columnName] = this[i];
     }
     return rowMap;
   }
@@ -580,7 +593,7 @@ class _PostgreSQLResultRow extends UnmodifiableListView
     final rowMap = <String, dynamic>{};
     for (var i = 0; i < _metaData.columnDescriptions.length; i++) {
       final col = _metaData.columnDescriptions[i];
-      rowMap[col.columnName] = this[i];
+      rowMap[col!.columnName] = this[i];
     }
     return rowMap;
   }
diff --git a/lib/src/connection_fsm.dart b/lib/src/connection_fsm.dart
index 3dbb2b4..11e939a 100644
--- a/lib/src/connection_fsm.dart
+++ b/lib/src/connection_fsm.dart
@@ -1,7 +1,7 @@
 part of postgres.connection;
 
 abstract class _PostgreSQLConnectionState {
-  PostgreSQLConnection connection;
+  PostgreSQLConnection? connection;
 
   _PostgreSQLConnectionState onEnter() {
     return this;
@@ -48,10 +48,10 @@ class _PostgreSQLConnectionStateSocketConnected
   @override
   _PostgreSQLConnectionState onEnter() {
     final startupMessage = StartupMessage(
-        connection.databaseName, connection.timeZone,
-        username: connection.username);
+        connection!.databaseName, connection!.timeZone,
+        username: connection!.username);
 
-    connection._socket.add(startupMessage.asBytes());
+    connection!._socket!.add(startupMessage.asBytes());
 
     return this;
   }
@@ -73,7 +73,7 @@ class _PostgreSQLConnectionStateSocketConnected
     if (authMessage.type == AuthenticationMessage.KindOK) {
       return _PostgreSQLConnectionStateAuthenticated(completer);
     } else if (authMessage.type == AuthenticationMessage.KindMD5Password) {
-      connection._salt = authMessage.salt;
+      connection!._salt = authMessage.salt;
 
       return _PostgreSQLConnectionStateAuthenticating(completer);
     }
@@ -98,9 +98,9 @@ class _PostgreSQLConnectionStateAuthenticating
   @override
   _PostgreSQLConnectionState onEnter() {
     final authMessage = AuthMD5Message(
-        connection.username, connection.password, connection._salt);
+        connection!.username!, connection!.password!, connection!._salt);
 
-    connection._socket.add(authMessage.asBytes());
+    connection!._socket!.add(authMessage.asBytes());
 
     return this;
   }
@@ -117,10 +117,10 @@ class _PostgreSQLConnectionStateAuthenticating
   @override
   _PostgreSQLConnectionState onMessage(ServerMessage message) {
     if (message is ParameterStatusMessage) {
-      connection.settings[message.name] = message.value;
+      connection!.settings[message.name] = message.value;
     } else if (message is BackendKeyMessage) {
-      connection._processID = message.processID;
-      connection._secretKey = message.secretKey;
+      connection!._processID = message.processID;
+      connection!._secretKey = message.secretKey;
     } else if (message is ReadyForQueryMessage) {
       if (message.state == ReadyForQueryMessage.StateIdle) {
         return _PostgreSQLConnectionStateIdle(openCompleter: completer);
@@ -153,10 +153,10 @@ class _PostgreSQLConnectionStateAuthenticated
   @override
   _PostgreSQLConnectionState onMessage(ServerMessage message) {
     if (message is ParameterStatusMessage) {
-      connection.settings[message.name] = message.value;
+      connection!.settings[message.name] = message.value;
     } else if (message is BackendKeyMessage) {
-      connection._processID = message.processID;
-      connection._secretKey = message.secretKey;
+      connection!._processID = message.processID;
+      connection!._secretKey = message.secretKey;
     } else if (message is ReadyForQueryMessage) {
       if (message.state == ReadyForQueryMessage.StateIdle) {
         return _PostgreSQLConnectionStateIdle(openCompleter: completer);
@@ -174,11 +174,11 @@ class _PostgreSQLConnectionStateAuthenticated
 class _PostgreSQLConnectionStateIdle extends _PostgreSQLConnectionState {
   _PostgreSQLConnectionStateIdle({this.openCompleter});
 
-  Completer openCompleter;
+  Completer? openCompleter;
 
   @override
   _PostgreSQLConnectionState awake() {
-    final pendingQuery = connection._queue.pending;
+    final pendingQuery = connection!._queue.pending;
     if (pendingQuery != null) {
       return processQuery(pendingQuery);
     }
@@ -189,18 +189,18 @@ class _PostgreSQLConnectionStateIdle extends _PostgreSQLConnectionState {
   _PostgreSQLConnectionState processQuery(Query<dynamic> q) {
     try {
       if (q.onlyReturnAffectedRowCount) {
-        q.sendSimple(connection._socket);
+        q.sendSimple(connection!._socket!);
         return _PostgreSQLConnectionStateBusy(q);
       }
 
-      final cached = connection._cache[q.statement];
-      q.sendExtended(connection._socket, cacheQuery: cached);
+      final cached = connection!._cache[q.statement];
+      q.sendExtended(connection!._socket!, cacheQuery: cached);
 
       return _PostgreSQLConnectionStateBusy(q);
     } catch (e, st) {
       scheduleMicrotask(() {
         q.completeError(e, st);
-        connection._transitionToState(_PostgreSQLConnectionStateIdle());
+        connection!._transitionToState(_PostgreSQLConnectionStateIdle());
       });
 
       return _PostgreSQLConnectionStateDeferredFailure();
@@ -228,7 +228,7 @@ class _PostgreSQLConnectionStateBusy extends _PostgreSQLConnectionState {
   _PostgreSQLConnectionStateBusy(this.query);
 
   Query<dynamic> query;
-  PostgreSQLException returningException;
+  PostgreSQLException? returningException;
   int rowsAffected = 0;
 
   @override
@@ -256,13 +256,12 @@ class _PostgreSQLConnectionStateBusy extends _PostgreSQLConnectionState {
 
     if (message is ReadyForQueryMessage) {
       if (message.state == ReadyForQueryMessage.StateTransactionError) {
-        query.completeError(returningException);
+        query.completeError(returningException!);
         return _PostgreSQLConnectionStateReadyInTransaction(
             query.transaction as _TransactionProxy);
       }
-
       if (returningException != null) {
-        query.completeError(returningException);
+        query.completeError(returningException!);
       } else {
         query.complete(rowsAffected);
       }
@@ -318,12 +317,12 @@ class _PostgreSQLConnectionStateReadyInTransaction
   _PostgreSQLConnectionState processQuery(Query<dynamic> q) {
     try {
       if (q.onlyReturnAffectedRowCount) {
-        q.sendSimple(connection._socket);
+        q.sendSimple(connection!._socket!);
         return _PostgreSQLConnectionStateBusy(q);
       }
 
-      final cached = connection._cache[q.statement];
-      q.sendExtended(connection._socket, cacheQuery: cached);
+      final cached = connection!._cache[q.statement];
+      q.sendExtended(connection!._socket!, cacheQuery: cached);
 
       return _PostgreSQLConnectionStateBusy(q);
     } catch (e, st) {
diff --git a/lib/src/exceptions.dart b/lib/src/exceptions.dart
index 44e6a00..33952e0 100644
--- a/lib/src/exceptions.dart
+++ b/lib/src/exceptions.dart
@@ -42,71 +42,71 @@ class PostgreSQLException implements Exception {
   PostgreSQLException._(List<ErrorField> errorFields, {this.stackTrace}) {
     final finder = (int identifer) => (errorFields.firstWhere(
         (ErrorField e) => e.identificationToken == identifer,
-        orElse: () => null));
+        orElse: () => ErrorField(null, null)));
 
     severity = ErrorField.severityFromString(
         finder(ErrorField.SeverityIdentifier).text);
     code = finder(ErrorField.CodeIdentifier).text;
     message = finder(ErrorField.MessageIdentifier).text;
-    detail = finder(ErrorField.DetailIdentifier)?.text;
-    hint = finder(ErrorField.HintIdentifier)?.text;
-
-    internalQuery = finder(ErrorField.InternalQueryIdentifier)?.text;
-    trace = finder(ErrorField.WhereIdentifier)?.text;
-    schemaName = finder(ErrorField.SchemaIdentifier)?.text;
-    tableName = finder(ErrorField.TableIdentifier)?.text;
-    columnName = finder(ErrorField.ColumnIdentifier)?.text;
-    dataTypeName = finder(ErrorField.DataTypeIdentifier)?.text;
-    constraintName = finder(ErrorField.ConstraintIdentifier)?.text;
-    fileName = finder(ErrorField.FileIdentifier)?.text;
-    routineName = finder(ErrorField.RoutineIdentifier)?.text;
-
-    var i = finder(ErrorField.PositionIdentifier)?.text;
+    detail = finder(ErrorField.DetailIdentifier).text;
+    hint = finder(ErrorField.HintIdentifier).text;
+
+    internalQuery = finder(ErrorField.InternalQueryIdentifier).text;
+    trace = finder(ErrorField.WhereIdentifier).text;
+    schemaName = finder(ErrorField.SchemaIdentifier).text;
+    tableName = finder(ErrorField.TableIdentifier).text;
+    columnName = finder(ErrorField.ColumnIdentifier).text;
+    dataTypeName = finder(ErrorField.DataTypeIdentifier).text;
+    constraintName = finder(ErrorField.ConstraintIdentifier).text;
+    fileName = finder(ErrorField.FileIdentifier).text;
+    routineName = finder(ErrorField.RoutineIdentifier).text;
+
+    var i = finder(ErrorField.PositionIdentifier).text;
     position = (i != null ? int.parse(i) : null);
 
-    i = finder(ErrorField.InternalPositionIdentifier)?.text;
+    i = finder(ErrorField.InternalPositionIdentifier).text;
     internalPosition = (i != null ? int.parse(i) : null);
 
-    i = finder(ErrorField.LineIdentifier)?.text;
+    i = finder(ErrorField.LineIdentifier).text;
     lineNumber = (i != null ? int.parse(i) : null);
   }
 
   /// The severity of the exception.
-  PostgreSQLSeverity severity;
+  PostgreSQLSeverity? severity;
 
   /// The PostgreSQL error code.
   ///
   /// May be null if the exception was not generated by the database.
-  String code;
+  String? code;
 
   /// A message indicating the error.
-  String message;
+  String? message;
 
   /// Additional details if provided by the database.
-  String detail;
+  String? detail;
 
   /// A hint on how to remedy an error, if provided by the database.
-  String hint;
+  String? hint;
 
   /// An index into an executed query string where an error occurred, if by provided by the database.
-  int position;
+  int? position;
 
   /// An index into a query string generated by the database, if provided.
-  int internalPosition;
-
-  String internalQuery;
-  String trace;
-  String schemaName;
-  String tableName;
-  String columnName;
-  String dataTypeName;
-  String constraintName;
-  String fileName;
-  int lineNumber;
-  String routineName;
+  int? internalPosition;
+
+  String? internalQuery;
+  String? trace;
+  String? schemaName;
+  String? tableName;
+  String? columnName;
+  String? dataTypeName;
+  String? constraintName;
+  String? fileName;
+  int? lineNumber;
+  String? routineName;
 
   /// A [StackTrace] if available.
-  StackTrace stackTrace;
+  StackTrace? stackTrace;
 
   @override
   String toString() {
diff --git a/lib/src/execution_context.dart b/lib/src/execution_context.dart
index c5f0e0e..a37d388 100644
--- a/lib/src/execution_context.dart
+++ b/lib/src/execution_context.dart
@@ -29,10 +29,10 @@ abstract class PostgreSQLExecutionContext {
   /// By default, instances of this class will reuse queries. This allows significantly more efficient transport to and from the database. You do not have to do
   /// anything to opt in to this behavior, this connection will track the necessary information required to reuse queries without intervention. (The [fmtString] is
   /// the unique identifier to look up reuse information.) You can disable reuse by passing false for [allowReuse].
-  Future<PostgreSQLResult> query(String fmtString,
+  Future<PostgreSQLResult?> query(String fmtString,
       {Map<String, dynamic> substitutionValues,
       bool allowReuse,
-      int timeoutInSeconds});
+      int? timeoutInSeconds});
 
   /// Executes a query on this context.
   ///
@@ -41,8 +41,8 @@ abstract class PostgreSQLExecutionContext {
   /// This method returns the number of rows affected and no additional information. This method uses the least efficient and less secure command
   /// for executing queries in the PostgreSQL protocol; [query] is preferred for queries that will be executed more than once, will contain user input,
   /// or return rows.
-  Future<int> execute(String fmtString,
-      {Map<String, dynamic> substitutionValues, int timeoutInSeconds});
+  Future<int?> execute(String fmtString,
+      {Map<String, dynamic> substitutionValues, int? timeoutInSeconds});
 
   /// Cancels a transaction on this context.
   ///
@@ -80,7 +80,7 @@ abstract class PostgreSQLExecutionContext {
   ///           "company: {"name": "stable|kernel"}
   ///         }
   ///       ]
-  Future<List<Map<String, Map<String, dynamic>>>> mappedResultsQuery(
+  Future<List<Map<String?, Map<String, dynamic>>>> mappedResultsQuery(
       String fmtString,
       {Map<String, dynamic> substitutionValues,
       bool allowReuse,
@@ -93,18 +93,18 @@ abstract class ColumnDescription {
   String get columnName;
 
   /// The resolved name of the referenced table.
-  String get tableName;
+  String? get tableName;
 }
 
 /// A single row of a query result.
 ///
 /// Column values can be accessed through the `[]` operator.
 abstract class PostgreSQLResultRow implements List {
-  List<ColumnDescription> get columnDescriptions;
+  List<ColumnDescription?> get columnDescriptions;
 
   /// Returns a two-level map that on the first level contains the resolved
   /// table name, and on the second level the column name (or its alias).
-  Map<String, Map<String, dynamic>> toTableColumnMap();
+  Map<String?, Map<String, dynamic>> toTableColumnMap();
 
   /// Returns a single-level map that maps the column name (or its alias) to the
   /// value returned on that position.
@@ -117,5 +117,5 @@ abstract class PostgreSQLResultRow implements List {
 abstract class PostgreSQLResult implements List<PostgreSQLResultRow> {
   /// How many rows did this query affect?
   int get affectedRowCount;
-  List<ColumnDescription> get columnDescriptions;
+  List<ColumnDescription?> get columnDescriptions;
 }
diff --git a/lib/src/message_window.dart b/lib/src/message_window.dart
index c40129a..91c47d6 100644
--- a/lib/src/message_window.dart
+++ b/lib/src/message_window.dart
@@ -30,8 +30,8 @@ class MessageFramer {
   final _reader = ByteDataReader();
   final messageQueue = Queue<ServerMessage>();
 
-  int _type;
-  int _expectedLength;
+  int? _type;
+  int _expectedLength = 0;
 
   bool get _hasReadHeader => _type != null;
   bool get _canReadHeader => _reader.remainingLength >= _headerByteSize;
@@ -59,7 +59,7 @@ class MessageFramer {
             msgMaker == null ? UnknownMessage(_type, data) : msgMaker(data);
         messageQueue.add(msg);
         _type = null;
-        _expectedLength = null;
+        _expectedLength = 0;
         evaluateNextMessage = true;
       }
     }
diff --git a/lib/src/query.dart b/lib/src/query.dart
index 26bd2d5..008f4fa 100644
--- a/lib/src/query.dart
+++ b/lib/src/query.dart
@@ -24,26 +24,26 @@ class Query<T> {
 
   final bool onlyReturnAffectedRowCount;
 
-  String statementIdentifier;
+  String? statementIdentifier;
 
-  Future<QueryResult<T>> get future => _onComplete.future;
+  Future<QueryResult<T>?> get future => _onComplete.future;
 
   final String statement;
-  final Map<String, dynamic> substitutionValues;
+  final Map<String, dynamic>? substitutionValues;
   final PostgreSQLExecutionContext transaction;
   final PostgreSQLConnection connection;
 
-  List<PostgreSQLDataType> _specifiedParameterTypeCodes;
+  late List<PostgreSQLDataType?> _specifiedParameterTypeCodes;
   final rows = <List<dynamic>>[];
 
-  CachedQuery cache;
+  CachedQuery? cache;
 
-  final _onComplete = Completer<QueryResult<T>>.sync();
-  List<FieldDescription> _fieldDescriptions;
+  final _onComplete = Completer<QueryResult<T>?>.sync();
+  List<FieldDescription>? _fieldDescriptions;
 
-  List<FieldDescription> get fieldDescriptions => _fieldDescriptions;
+  List<FieldDescription>? get fieldDescriptions => _fieldDescriptions;
 
-  set fieldDescriptions(List<FieldDescription> fds) {
+  set fieldDescriptions(List<FieldDescription>? fds) {
     _fieldDescriptions = fds;
     cache?.fieldDescriptions = fds;
   }
@@ -56,9 +56,9 @@ class Query<T> {
     socket.add(queryMessage.asBytes());
   }
 
-  void sendExtended(Socket socket, {CachedQuery cacheQuery}) {
+  void sendExtended(Socket socket, {CachedQuery? cacheQuery}) {
     if (cacheQuery != null) {
-      fieldDescriptions = cacheQuery.fieldDescriptions;
+      fieldDescriptions = cacheQuery.fieldDescriptions!;
       sendCachedQuery(socket, cacheQuery, substitutionValues);
 
       return;
@@ -89,21 +89,21 @@ class Query<T> {
     ];
 
     if (statementIdentifier != null) {
-      cache = CachedQuery(statementIdentifier, formatIdentifiers);
+      cache = CachedQuery(statementIdentifier!, formatIdentifiers);
     }
 
     socket.add(ClientMessage.aggregateBytes(messages));
   }
 
   void sendCachedQuery(Socket socket, CachedQuery cacheQuery,
-      Map<String, dynamic> substitutionValues) {
+      Map<String, dynamic>? substitutionValues) {
     final statementName = cacheQuery.preparedStatementName;
-    final parameterList = cacheQuery.orderedParameters
+    final parameterList = cacheQuery.orderedParameters!
         .map((identifier) => ParameterValue(identifier, substitutionValues))
         .toList();
 
     final bytes = ClientMessage.aggregateBytes([
-      BindMessage(parameterList, statementName: statementName),
+      BindMessage(parameterList, statementName: statementName!),
       ExecuteMessage(),
       SyncMessage()
     ]);
@@ -111,7 +111,7 @@ class Query<T> {
     socket.add(bytes);
   }
 
-  PostgreSQLException validateParameters(List<int> parameterTypeIDs) {
+  PostgreSQLException? validateParameters(List<int> parameterTypeIDs) {
     final actualParameterTypeCodeIterator = parameterTypeIDs.iterator;
     final parametersAreMismatched =
         _specifiedParameterTypeCodes.map((specifiedType) {
@@ -134,12 +134,12 @@ class Query<T> {
     return null;
   }
 
-  void addRow(List<Uint8List> rawRowData) {
-    if (onlyReturnAffectedRowCount) {
+  void addRow(List<Uint8List?> rawRowData) {
+    if (onlyReturnAffectedRowCount || fieldDescriptions == null) {
       return;
     }
 
-    final iterator = fieldDescriptions.iterator;
+    final iterator = fieldDescriptions!.iterator;
     final lazyDecodedData = rawRowData.map((bd) {
       iterator.moveNext();
       return iterator.current.converter.convert(bd);
@@ -161,7 +161,7 @@ class Query<T> {
     _onComplete.complete(QueryResult(rowsAffected, rows as T));
   }
 
-  void completeError(dynamic error, [StackTrace stackTrace]) {
+  void completeError(Object error, [StackTrace? stackTrace]) {
     if (_onComplete.isCompleted) {
       return;
     }
@@ -175,7 +175,7 @@ class Query<T> {
 
 class QueryResult<T> {
   final int affectedRowCount;
-  final T value;
+  final T? value;
 
   const QueryResult(this.affectedRowCount, this.value);
 }
@@ -183,9 +183,9 @@ class QueryResult<T> {
 class CachedQuery {
   CachedQuery(this.preparedStatementName, this.orderedParameters);
 
-  final String preparedStatementName;
-  final List<PostgreSQLFormatIdentifier> orderedParameters;
-  List<FieldDescription> fieldDescriptions;
+  final String? preparedStatementName;
+  final List<PostgreSQLFormatIdentifier>? orderedParameters;
+  List<FieldDescription>? fieldDescriptions;
 
   bool get isValid {
     return preparedStatementName != null &&
@@ -196,13 +196,13 @@ class CachedQuery {
 
 class ParameterValue {
   factory ParameterValue(PostgreSQLFormatIdentifier identifier,
-      Map<String, dynamic> substitutionValues) {
+      Map<String, dynamic>? substitutionValues) {
     if (identifier.type == null) {
-      return ParameterValue.text(substitutionValues[identifier.name]);
+      return ParameterValue.text(substitutionValues?[identifier.name]);
     }
 
     return ParameterValue.binary(
-        substitutionValues[identifier.name], identifier.type);
+        substitutionValues?[identifier.name], identifier.type!);
   }
 
   factory ParameterValue.binary(
@@ -214,7 +214,7 @@ class ParameterValue {
   }
 
   factory ParameterValue.text(dynamic value) {
-    Uint8List bytes;
+    Uint8List? bytes;
     if (value != null) {
       final converter = PostgresTextEncoder();
       bytes = castBytes(
@@ -227,7 +227,7 @@ class ParameterValue {
   ParameterValue._(this.isBinary, this.bytes, this.length);
 
   final bool isBinary;
-  final Uint8List bytes;
+  final Uint8List? bytes;
   final int length;
 }
 
@@ -244,7 +244,7 @@ class FieldDescription implements ColumnDescription {
   final int formatCode;
 
   @override
-  final String tableName;
+  final String? tableName;
 
   FieldDescription._(
     this.converter,
@@ -285,7 +285,7 @@ class FieldDescription implements ColumnDescription {
     );
   }
 
-  FieldDescription change({String tableName}) {
+  FieldDescription change({String? tableName}) {
     return FieldDescription._(converter, columnName, tableID, columnID, typeID,
         dataTypeSize, typeModifier, formatCode, tableName ?? this.tableName);
   }
@@ -328,8 +328,8 @@ class PostgreSQLFormatIdentifier {
 
   factory PostgreSQLFormatIdentifier(String t) {
     String name;
-    PostgreSQLDataType type;
-    String typeCast;
+    PostgreSQLDataType? type;
+    String? typeCast;
 
     final components = t.split('::');
     if (components.length > 1) {
@@ -343,12 +343,11 @@ class PostgreSQLFormatIdentifier {
       name = variableComponents.first;
 
       final dataTypeString = variableComponents.last;
-      if (dataTypeString != null) {
-        type = typeStringToCodeMap[dataTypeString];
-        if (type == null) {
-          throw FormatException(
-              "Invalid type code in substitution variable '$t'");
-        }
+      try {
+        type = typeStringToCodeMap[dataTypeString]!;
+      } catch (e) {
+        throw FormatException(
+            "Invalid type code in substitution variable '$t'");
       }
     } else {
       throw FormatException(
@@ -363,6 +362,6 @@ class PostgreSQLFormatIdentifier {
   PostgreSQLFormatIdentifier._(this.name, this.type, this.typeCast);
 
   final String name;
-  final PostgreSQLDataType type;
-  final String typeCast;
+  final PostgreSQLDataType? type;
+  final String? typeCast;
 }
diff --git a/lib/src/query_cache.dart b/lib/src/query_cache.dart
index 2acf5d9..4fa4690 100644
--- a/lib/src/query_cache.dart
+++ b/lib/src/query_cache.dart
@@ -12,12 +12,12 @@ class QueryCache {
       return;
     }
 
-    if (query.cache.isValid) {
-      _queries[query.statement] = query.cache;
+    if (query.cache!.isValid) {
+      _queries[query.statement] = query.cache!;
     }
   }
 
-  CachedQuery operator [](String statementId) {
+  CachedQuery? operator [](String? statementId) {
     if (statementId == null) {
       return null;
     }
@@ -28,7 +28,7 @@ class QueryCache {
   String identifierForQuery(Query<dynamic> query) {
     final existing = _queries[query.statement];
     if (existing != null) {
-      return existing.preparedStatementName;
+      return existing.preparedStatementName!;
     }
 
     final string = '$_idCounter'.padLeft(12, '0');
diff --git a/lib/src/query_queue.dart b/lib/src/query_queue.dart
index 29514cb..42ac683 100644
--- a/lib/src/query_queue.dart
+++ b/lib/src/query_queue.dart
@@ -13,14 +13,14 @@ class QueryQueue extends ListBase<Query<dynamic>>
   PostgreSQLException get _cancellationException => PostgreSQLException(
       'Query cancelled due to the database connection closing.');
 
-  Query<dynamic> get pending {
+  Query<dynamic>? get pending {
     if (_inner.isEmpty) {
       return null;
     }
     return _inner.first;
   }
 
-  void cancel([dynamic error, StackTrace stackTrace]) {
+  void cancel([Object? error, StackTrace? stackTrace]) {
     _isCancelled = true;
     error ??= _cancellationException;
     final existing = _inner;
@@ -30,8 +30,8 @@ class QueryQueue extends ListBase<Query<dynamic>>
     // get the error and not the close message, since completeError is
     // synchronous.
     scheduleMicrotask(() {
-      existing?.forEach((q) {
-        q.completeError(error, stackTrace);
+      existing.forEach((q) {
+        q.completeError(error!, stackTrace);
       });
     });
   }
diff --git a/lib/src/server_messages.dart b/lib/src/server_messages.dart
index 4ee1f9a..709a659 100644
--- a/lib/src/server_messages.dart
+++ b/lib/src/server_messages.dart
@@ -14,8 +14,8 @@ class ErrorResponseMessage implements ServerMessage {
   ErrorResponseMessage(Uint8List bytes) {
     final reader = ByteDataReader()..add(bytes);
 
-    int identificationToken;
-    StringBuffer sb;
+    int? identificationToken;
+    StringBuffer? sb;
 
     while (reader.remainingLength > 0) {
       final byte = reader.readUint8();
@@ -27,7 +27,7 @@ class ErrorResponseMessage implements ServerMessage {
         identificationToken = null;
         sb = null;
       } else {
-        sb.writeCharCode(byte);
+        sb!.writeCharCode(byte);
       }
     }
     if (identificationToken != null && sb != null) {
@@ -54,9 +54,9 @@ class AuthenticationMessage implements ServerMessage {
   factory AuthenticationMessage(Uint8List bytes) {
     final reader = ByteDataReader()..add(bytes);
     final type = reader.readUint32();
-    List<int> salt;
+    final salt = <int>[];
     if (type == KindMD5Password) {
-      salt = reader.read(4, copy: true);
+      salt.addAll(reader.read(4, copy: true));
     }
     return AuthenticationMessage._(type, salt);
   }
@@ -115,7 +115,7 @@ class RowDescriptionMessage extends ServerMessage {
 }
 
 class DataRowMessage extends ServerMessage {
-  final values = <Uint8List>[];
+  final values = <Uint8List?>[];
 
   DataRowMessage(Uint8List bytes) {
     final reader = ByteDataReader()..add(bytes);
@@ -168,7 +168,7 @@ class CommandCompleteMessage extends ServerMessage {
     final str = utf8.decode(bytes.sublist(0, bytes.length - 1));
     final match = identifierExpression.firstMatch(str);
     var rowsAffected = 0;
-    if (match.end < str.length) {
+    if (match != null && match.end < str.length) {
       rowsAffected = int.parse(str.split(' ').last);
     }
     return CommandCompleteMessage._(rowsAffected);
@@ -210,8 +210,8 @@ class NoDataMessage extends ServerMessage {
 }
 
 class UnknownMessage extends ServerMessage {
-  final int code;
-  final Uint8List bytes;
+  final int? code;
+  final Uint8List? bytes;
 
   UnknownMessage(this.code, this.bytes);
 
@@ -223,11 +223,11 @@ class UnknownMessage extends ServerMessage {
   @override
   bool operator ==(dynamic other) {
     if (bytes != null) {
-      if (bytes.length != other.bytes.length) {
+      if (bytes!.length != other.bytes.length) {
         return false;
       }
-      for (var i = 0; i < bytes.length; i++) {
-        if (bytes[i] != other.bytes[i]) {
+      for (var i = 0; i < bytes!.length; i++) {
+        if (bytes![i] != other.bytes[i]) {
           return false;
         }
       }
@@ -259,7 +259,7 @@ class ErrorField {
   static const int LineIdentifier = 76;
   static const int RoutineIdentifier = 82;
 
-  static PostgreSQLSeverity severityFromString(String str) {
+  static PostgreSQLSeverity severityFromString(String? str) {
     switch (str) {
       case 'ERROR':
         return PostgreSQLSeverity.error;
@@ -277,13 +277,13 @@ class ErrorField {
         return PostgreSQLSeverity.info;
       case 'LOG':
         return PostgreSQLSeverity.log;
+      default:
+        return PostgreSQLSeverity.unknown;
     }
-
-    return PostgreSQLSeverity.unknown;
   }
 
-  final int identificationToken;
-  final String text;
+  final int? identificationToken;
+  final String? text;
 
   ErrorField(this.identificationToken, this.text);
 }
diff --git a/lib/src/substituter.dart b/lib/src/substituter.dart
index 0d7f647..472383f 100644
--- a/lib/src/substituter.dart
+++ b/lib/src/substituter.dart
@@ -5,7 +5,7 @@ import 'types.dart';
 class PostgreSQLFormat {
   static final int _atSignCodeUnit = '@'.codeUnitAt(0);
 
-  static String id(String name, {PostgreSQLDataType type}) {
+  static String id(String name, {PostgreSQLDataType? type}) {
     if (type != null) {
       return '@$name:${dataTypeStringForDataType(type)}';
     }
@@ -13,7 +13,7 @@ class PostgreSQLFormat {
     return '@$name';
   }
 
-  static String dataTypeStringForDataType(PostgreSQLDataType dt) {
+  static String? dataTypeStringForDataType(PostgreSQLDataType? dt) {
     switch (dt) {
       case PostgreSQLDataType.text:
         return 'text';
@@ -47,19 +47,19 @@ class PostgreSQLFormat {
         return 'name';
       case PostgreSQLDataType.uuid:
         return 'uuid';
+      default:
+        return null;
     }
-
-    return null;
   }
 
-  static String substitute(String fmtString, Map<String, dynamic> values,
-      {SQLReplaceIdentifierFunction replace}) {
+  static String substitute(String fmtString, Map<String, dynamic>? values,
+      {SQLReplaceIdentifierFunction? replace}) {
     final converter = PostgresTextEncoder();
-    values ??= <String, dynamic>{};
-    replace ??= (spec, index) => converter.convert(values[spec.name]);
+    values ??= const {};
+    replace ??= (spec, index) => converter.convert(values![spec.name]);
 
     final items = <PostgreSQLFormatToken>[];
-    PostgreSQLFormatToken currentPtr;
+    PostgreSQLFormatToken? currentPtr;
     final iterator = RuneIterator(fmtString);
 
     while (iterator.moveNext()) {
@@ -115,13 +115,13 @@ class PostgreSQLFormat {
       } else {
         final identifier = PostgreSQLFormatIdentifier(t.buffer.toString());
 
-        if (!values.containsKey(identifier.name)) {
+        if (values != null && !values.containsKey(identifier.name)) {
           // Format string specified identifier with name ${identifier.name},
           // but key was not present in values.
           return t.buffer;
         }
 
-        final val = replace(identifier, idx);
+        final val = replace!(identifier, idx);
         idx++;
 
         if (identifier.typeCast != null) {
diff --git a/lib/src/text_codec.dart b/lib/src/text_codec.dart
index 852f986..8eca302 100644
--- a/lib/src/text_codec.dart
+++ b/lib/src/text_codec.dart
@@ -110,7 +110,7 @@ class PostgresTextEncoder {
     return value ? 'TRUE' : 'FALSE';
   }
 
-  String _encodeDateTime(DateTime value, {bool isDateOnly}) {
+  String _encodeDateTime(DateTime value, {bool isDateOnly = false}) {
     var string = value.toIso8601String();
 
     if (isDateOnly) {
diff --git a/lib/src/transaction_proxy.dart b/lib/src/transaction_proxy.dart
index 67ea2b1..077345f 100644
--- a/lib/src/transaction_proxy.dart
+++ b/lib/src/transaction_proxy.dart
@@ -13,12 +13,12 @@ class _TransactionProxy extends Object
 
     _beginQuery.future.then(startTransaction).catchError((err, StackTrace st) {
       Future(() {
-        _completer.completeError(err, st);
+        _completer.completeError(err as Object, st);
       });
     });
   }
 
-  Query<dynamic> _beginQuery;
+  late Query<dynamic> _beginQuery;
   final _completer = Completer();
 
   Future get future => _completer.future;
@@ -30,13 +30,13 @@ class _TransactionProxy extends Object
   PostgreSQLExecutionContext get _transaction => this;
 
   final _TransactionQuerySignature executionBlock;
-  final int commitTimeoutInSeconds;
+  final int? commitTimeoutInSeconds;
   bool _hasFailed = false;
   bool _hasRolledBack = false;
 
   @override
-  void cancelTransaction({String reason}) {
-    throw _TransactionRollbackException(reason);
+  void cancelTransaction({String? reason}) {
+    throw _TransactionRollbackException(reason ?? 'Reason not given.');
   }
 
   Future startTransaction(dynamic _) async {
@@ -70,7 +70,7 @@ class _TransactionProxy extends Object
     }
   }
 
-  Future _cancelAndRollback(dynamic object, [StackTrace trace]) async {
+  Future _cancelAndRollback(dynamic object, [StackTrace? trace]) async {
     if (_hasRolledBack) {
       return;
     }
@@ -102,11 +102,11 @@ class _TransactionProxy extends Object
     if (object is _TransactionRollbackException) {
       _completer.complete(PostgreSQLRollback._(object.reason));
     } else {
-      _completer.completeError(object, trace);
+      _completer.completeError(object as Object, trace);
     }
   }
 
-  Future _transactionFailed(dynamic error, [StackTrace trace]) async {
+  Future _transactionFailed(dynamic error, [StackTrace? trace]) async {
     if (_hasFailed) {
       return;
     }
@@ -117,7 +117,7 @@ class _TransactionProxy extends Object
   }
 
   @override
-  Future _onQueryError(Query query, dynamic error, [StackTrace trace]) {
+  Future _onQueryError(Query query, dynamic error, [StackTrace? trace]) {
     return _transactionFailed(error, trace);
   }
 }
diff --git a/lib/src/utf8_backed_string.dart b/lib/src/utf8_backed_string.dart
index 360344d..f8612e8 100644
--- a/lib/src/utf8_backed_string.dart
+++ b/lib/src/utf8_backed_string.dart
@@ -3,7 +3,7 @@ import 'dart:convert';
 class UTF8BackedString {
   UTF8BackedString(this.string);
 
-  List<int> _cachedUTF8Bytes;
+  List<int>? _cachedUTF8Bytes;
 
   bool get hasCachedBytes => _cachedUTF8Bytes != null;
 
@@ -11,11 +11,11 @@ class UTF8BackedString {
 
   int get utf8Length {
     _cachedUTF8Bytes ??= utf8.encode(string);
-    return _cachedUTF8Bytes.length;
+    return _cachedUTF8Bytes!.length;
   }
 
   List<int> get utf8Bytes {
     _cachedUTF8Bytes ??= utf8.encode(string);
-    return _cachedUTF8Bytes;
+    return _cachedUTF8Bytes!;
   }
 }
diff --git a/pubspec.yaml b/pubspec.yaml
index 48ef18e..8de7278 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,16 +1,16 @@
 name: postgres
 description: PostgreSQL database driver. Supports statement reuse and binary protocol.
-version: 2.2.0
+version: 2.3.0
 homepage: https://github.com/stablekernel/postgresql-dart
 
 environment:
-  sdk: ">=2.8.0 <3.0.0"
+  sdk: ">=2.12.0-0 <3.0.0"
 
 dependencies:
-  buffer: ^1.0.6
-  crypto: ^2.0.0
+  buffer: ^1.1.0-nullsafety.0
+  crypto: ^3.0.0
 
 dev_dependencies:
-  pedantic: ^1.0.0
-  test: ^1.3.0
+  pedantic: ^1.10.0
+  test: ^1.16.3
   coverage: any
diff --git a/test/connection_test.dart b/test/connection_test.dart
index d95b7d0..48c87a7 100644
--- a/test/connection_test.dart
+++ b/test/connection_test.dart
@@ -10,10 +10,10 @@ import 'package:postgres/postgres.dart';
 
 void main() {
   group('Connection lifecycle', () {
-    PostgreSQLConnection conn;
+    late PostgreSQLConnection conn;
 
     tearDown(() async {
-      await conn?.close();
+      await conn.close();
     });
 
     test('Connect with md5 auth required', () async {
@@ -70,8 +70,6 @@ void main() {
       final underlyingSocket =
           reflect(conn).getField(socketMirror.simpleName).reflectee as Socket;
       expect(await underlyingSocket.done, isNotNull);
-
-      conn = null;
     });
 
     test('SSL Closing idle connection succeeds, closes underlying socket',
@@ -88,8 +86,6 @@ void main() {
       final underlyingSocket =
           reflect(conn).getField(socketMirror.simpleName).reflectee as Socket;
       expect(await underlyingSocket.done, isNotNull);
-
-      conn = null;
     });
 
     test(
@@ -148,7 +144,7 @@ void main() {
   });
 
   group('Successful queries over time', () {
-    PostgreSQLConnection conn;
+    late PostgreSQLConnection conn;
 
     setUp(() async {
       conn = PostgreSQLConnection('localhost', 5432, 'dart_test',
@@ -157,7 +153,7 @@ void main() {
     });
 
     tearDown(() async {
-      await conn?.close();
+      await conn.close();
     });
 
     test(
@@ -224,12 +220,12 @@ void main() {
   });
 
   group('Unintended user-error situations', () {
-    PostgreSQLConnection conn;
-    Future openFuture;
+    late PostgreSQLConnection conn;
+    late Future openFuture;
 
     tearDown(() async {
       await openFuture;
-      await conn?.close();
+      await conn.close();
     });
 
     test('Sending queries to opening connection triggers error', () async {
@@ -348,7 +344,6 @@ void main() {
       await conn.execute('CREATE TEMPORARY TABLE t (i int unique)');
 
       await conn.execute('INSERT INTO t (i) VALUES (1)');
-      //ignore: unawaited_futures
       conn.execute('INSERT INTO t (i) VALUES (1)').catchError((err) {
         // ignore
       });
@@ -393,7 +388,6 @@ void main() {
       final orderEnsurer = [];
 
       // this will emit a query error
-      //ignore: unawaited_futures
       conn.execute('INSERT INTO t (i) VALUES (1)').catchError((err) {
         orderEnsurer.add(1);
         // ignore
@@ -449,12 +443,16 @@ void main() {
   });
 
   group('Network error situations', () {
-    ServerSocket serverSocket;
-    Socket socket;
+    ServerSocket? serverSocket;
+    Socket? socket;
 
     tearDown(() async {
-      await serverSocket?.close();
-      await socket?.close();
+      if (serverSocket != null) {
+        await serverSocket!.close();
+      }
+      if (socket != null) {
+        await socket!.close();
+      }
     });
 
     test(
@@ -493,7 +491,7 @@ void main() {
         () async {
       serverSocket =
           await ServerSocket.bind(InternetAddress.loopbackIPv4, 5433);
-      serverSocket.listen((s) {
+      serverSocket!.listen((s) {
         socket = s;
         // Don't respond on purpose
         s.listen((bytes) {});
@@ -517,7 +515,7 @@ void main() {
         () async {
       serverSocket =
           await ServerSocket.bind(InternetAddress.loopbackIPv4, 5433);
-      serverSocket.listen((s) {
+      serverSocket!.listen((s) {
         socket = s;
         // Don't respond on purpose
         s.listen((bytes) {});
@@ -541,7 +539,7 @@ void main() {
       final openCompleter = Completer();
       serverSocket =
           await ServerSocket.bind(InternetAddress.loopbackIPv4, 5433);
-      serverSocket.listen((s) {
+      serverSocket!.listen((s) {
         socket = s;
         // Don't respond on purpose
         s.listen((bytes) {});
@@ -567,7 +565,7 @@ void main() {
       final openCompleter = Completer();
       serverSocket =
           await ServerSocket.bind(InternetAddress.loopbackIPv4, 5433);
-      serverSocket.listen((s) {
+      serverSocket!.listen((s) {
         socket = s;
         // Don't respond on purpose
         s.listen((bytes) {});
diff --git a/test/decode_test.dart b/test/decode_test.dart
index 27096fb..f492f0b 100644
--- a/test/decode_test.dart
+++ b/test/decode_test.dart
@@ -2,7 +2,7 @@ import 'package:postgres/postgres.dart';
 import 'package:test/test.dart';
 
 void main() {
-  PostgreSQLConnection connection;
+  late PostgreSQLConnection connection;
   setUp(() async {
     connection = PostgreSQLConnection('localhost', 5432, 'dart_test',
         username: 'dart', password: 'dart');
@@ -34,13 +34,13 @@ void main() {
         'VALUES (null, null, null, null, null, null, null, null, null, null, null, null, null)');
   });
   tearDown(() async {
-    await connection?.close();
+    await connection.close();
   });
 
   test('Fetch em', () async {
     final res = await connection.query('select * from t');
 
-    final row1 = res[0];
+    final row1 = res![0];
     final row2 = res[1];
     final row3 = res[2];
 
diff --git a/test/encoding_test.dart b/test/encoding_test.dart
index edfc81e..3566d7e 100644
--- a/test/encoding_test.dart
+++ b/test/encoding_test.dart
@@ -9,7 +9,7 @@ import 'package:postgres/src/text_codec.dart';
 import 'package:postgres/src/types.dart';
 import 'package:postgres/src/utf8_backed_string.dart';
 
-PostgreSQLConnection conn;
+late PostgreSQLConnection conn;
 
 void main() {
   group('Binary encoders', () {
@@ -21,7 +21,6 @@ void main() {
 
     tearDown(() async {
       await conn.close();
-      conn = null;
     });
 
     // expectInverse ensures that:
@@ -394,7 +393,7 @@ Future expectInverse(dynamic value, PostgreSQLDataType dataType) async {
   final result = await conn.query(
       'INSERT INTO t (v) VALUES (${PostgreSQLFormat.id('v', type: dataType)}) RETURNING v',
       substitutionValues: {'v': value});
-  expect(result.first.first, equals(value));
+  expect(result!.first.first, equals(value));
 
   final encoder = PostgresBinaryEncoder(dataType);
   final encodedValue = encoder.convert(value);
@@ -404,7 +403,7 @@ Future expectInverse(dynamic value, PostgreSQLDataType dataType) async {
   } else if (dataType == PostgreSQLDataType.bigSerial) {
     dataType = PostgreSQLDataType.bigInteger;
   }
-  int code;
+  late int code;
   PostgresBinaryDecoder.typeMap.forEach((key, type) {
     if (type == dataType) {
       code = key;
diff --git a/test/framer_test.dart b/test/framer_test.dart
index 77a3996..064c54e 100644
--- a/test/framer_test.dart
+++ b/test/framer_test.dart
@@ -8,7 +8,7 @@ import 'package:postgres/src/message_window.dart';
 import 'package:postgres/src/server_messages.dart';
 
 void main() {
-  MessageFramer framer;
+  late MessageFramer framer;
   setUp(() {
     framer = MessageFramer();
   });
diff --git a/test/json_test.dart b/test/json_test.dart
index cee5b27..c045c32 100644
--- a/test/json_test.dart
+++ b/test/json_test.dart
@@ -2,7 +2,7 @@ import 'package:postgres/postgres.dart';
 import 'package:test/test.dart';
 
 void main() {
-  PostgreSQLConnection connection;
+  late PostgreSQLConnection connection;
 
   setUp(() async {
     connection = PostgreSQLConnection('localhost', 5432, 'dart_test',
@@ -15,7 +15,7 @@ void main() {
   });
 
   tearDown(() async {
-    await connection?.close();
+    await connection.close();
   });
 
   group('Storage', () {
diff --git a/test/map_return_test.dart b/test/map_return_test.dart
index b0135ed..ac2e222 100644
--- a/test/map_return_test.dart
+++ b/test/map_return_test.dart
@@ -4,7 +4,7 @@ import 'package:postgres/postgres.dart';
 import 'package:test/test.dart';
 
 void main() {
-  PostgreSQLConnection connection;
+  late PostgreSQLConnection connection;
 
   setUp(() async {
     connection = PostgreSQLConnection('localhost', 5432, 'dart_test',
@@ -31,7 +31,7 @@ void main() {
   });
 
   tearDown(() async {
-    await connection?.close();
+    await connection.close();
   });
 
   test('Get row map without specifying columns', () async {
diff --git a/test/notification_test.dart b/test/notification_test.dart
index d6cb5d9..d12aaae 100644
--- a/test/notification_test.dart
+++ b/test/notification_test.dart
@@ -5,9 +5,7 @@ import 'package:test/test.dart';
 
 void main() {
   group('Successful notifications', () {
-    var connection = PostgreSQLConnection('localhost', 5432, 'dart_test',
-        username: 'dart', password: 'dart');
-
+    late PostgreSQLConnection connection;
     setUp(() async {
       connection = PostgreSQLConnection('localhost', 5432, 'dart_test',
           username: 'dart', password: 'dart');
diff --git a/test/query_reuse_test.dart b/test/query_reuse_test.dart
index 44ebbae..929cb6a 100644
--- a/test/query_reuse_test.dart
+++ b/test/query_reuse_test.dart
@@ -11,7 +11,7 @@ String sid(String id, PostgreSQLDataType dt) =>
 
 void main() {
   group('Retaining type information', () {
-    PostgreSQLConnection connection;
+    late PostgreSQLConnection connection;
 
     setUp(() async {
       connection = PostgreSQLConnection('localhost', 5432, 'dart_test',
@@ -281,7 +281,7 @@ void main() {
   });
 
   group('Mixing prepared statements', () {
-    PostgreSQLConnection connection;
+    late PostgreSQLConnection connection;
 
     setUp(() async {
       connection = PostgreSQLConnection('localhost', 5432, 'dart_test',
@@ -440,8 +440,7 @@ void main() {
   });
 
   group('Failure cases', () {
-    var connection = PostgreSQLConnection('localhost', 5432, 'dart_test',
-        username: 'dart', password: 'dart');
+    late PostgreSQLConnection connection;
 
     setUp(() async {
       connection = PostgreSQLConnection('localhost', 5432, 'dart_test',
diff --git a/test/query_test.dart b/test/query_test.dart
index 9627632..8ee2244 100644
--- a/test/query_test.dart
+++ b/test/query_test.dart
@@ -4,8 +4,7 @@ import 'package:postgres/src/types.dart';
 
 void main() {
   group('Successful queries', () {
-    var connection = PostgreSQLConnection('localhost', 5432, 'dart_test',
-        username: 'dart', password: 'dart');
+    late PostgreSQLConnection connection;
 
     setUp(() async {
       connection = PostgreSQLConnection('localhost', 5432, 'dart_test',
@@ -39,9 +38,9 @@ void main() {
       expect(result, [expectedRow]);
 
       result = await connection.query('select t from t');
-      expect(result.columnDescriptions, hasLength(1));
-      expect(result.columnDescriptions.single.tableName, 't');
-      expect(result.columnDescriptions.single.columnName, 't');
+      expect(result!.columnDescriptions, hasLength(1));
+      expect(result.columnDescriptions.single!.tableName, 't');
+      expect(result.columnDescriptions.single!.columnName, 't');
       expect(result, [expectedRow]);
     });
 
@@ -155,11 +154,11 @@ void main() {
         {'a': 'b'},
         '01234567-89ab-cdef-0123-0123456789ab'
       ];
-      expect(result.columnDescriptions, hasLength(14));
-      expect(result.columnDescriptions.first.tableName, 't');
-      expect(result.columnDescriptions.first.columnName, 'i');
-      expect(result.columnDescriptions.last.tableName, 't');
-      expect(result.columnDescriptions.last.columnName, 'u');
+      expect(result!.columnDescriptions, hasLength(14));
+      expect(result.columnDescriptions.first!.tableName, 't');
+      expect(result.columnDescriptions.first!.columnName, 'i');
+      expect(result.columnDescriptions.last!.tableName, 't');
+      expect(result.columnDescriptions.last!.columnName, 'u');
       expect(result, [expectedRow]);
       result = await connection.query(
           'select i,s, bi, bs, bl, si, t, f, d, dt, ts, tsz, j, u from t');
@@ -332,8 +331,7 @@ void main() {
   });
 
   group('Unsuccesful queries', () {
-    var connection = PostgreSQLConnection('localhost', 5432, 'dart_test',
-        username: 'dart', password: 'dart');
+    late PostgreSQLConnection connection;
 
     setUp(() async {
       connection = PostgreSQLConnection('localhost', 5432, 'dart_test',
@@ -365,13 +363,13 @@ void main() {
         () async {
       final rs1 = await connection
           .query('SELECT *  FROM (VALUES (\'user@domain.com\')) t1 (col1)');
-      expect(rs1.first.toColumnMap(), {'col1': 'user@domain.com'});
+      expect(rs1!.first.toColumnMap(), {'col1': 'user@domain.com'});
 
       final rs2 = await connection.query(
         'SELECT *  FROM (VALUES (\'user@domain.com\')) t1 (col1) WHERE col1 > @u1',
         substitutionValues: {'u1': 'hello@domain.com'},
       );
-      expect(rs2.first.toColumnMap(), {'col1': 'user@domain.com'});
+      expect(rs2!.first.toColumnMap(), {'col1': 'user@domain.com'});
     });
 
     test('Wrong type for parameter in substitution values fails', () async {
diff --git a/test/timeout_test.dart b/test/timeout_test.dart
index 5ff8f32..610db5f 100644
--- a/test/timeout_test.dart
+++ b/test/timeout_test.dart
@@ -5,7 +5,7 @@ import 'package:test/test.dart';
 import 'package:postgres/postgres.dart';
 
 void main() {
-  PostgreSQLConnection conn;
+  late PostgreSQLConnection conn;
 
   setUp(() async {
     conn = PostgreSQLConnection('localhost', 5432, 'dart_test',
@@ -15,7 +15,7 @@ void main() {
   });
 
   tearDown(() async {
-    await conn?.close();
+    await conn.close();
   });
 
   test(
diff --git a/test/transaction_test.dart b/test/transaction_test.dart
index e588032..5bee2ef 100644
--- a/test/transaction_test.dart
+++ b/test/transaction_test.dart
@@ -7,7 +7,7 @@ import 'package:postgres/postgres.dart';
 
 void main() {
   group('Transaction behavior', () {
-    PostgreSQLConnection conn;
+    late PostgreSQLConnection conn;
 
     setUp(() async {
       conn = PostgreSQLConnection('localhost', 5432, 'dart_test',
@@ -17,7 +17,7 @@ void main() {
     });
 
     tearDown(() async {
-      await conn?.close();
+      await conn.close();
     });
 
     test('Rows are Lists of column values', () async {
@@ -248,8 +248,12 @@ void main() {
         () async {
       final errs = [];
       await conn.transaction((ctx) async {
-        ctx.query('INSERT INTO t (id) VALUES (1)').catchError(errs.add);
-        ctx.query('INSERT INTO t (id) VALUES (2)').catchError(errs.add);
+        final errsAdd = (e) {
+          errs.add(e);
+          return null;
+        };
+        ctx.query('INSERT INTO t (id) VALUES (1)').catchError(errsAdd);
+        ctx.query('INSERT INTO t (id) VALUES (2)').catchError(errsAdd);
         ctx.cancelTransaction();
         ctx.query('INSERT INTO t (id) VALUES (3)').catchError((e) {});
       });
@@ -295,7 +299,7 @@ void main() {
   // After a transaction fails, the changes must be rolled back, it should continue with pending queries, pending transactions, later queries, later transactions
 
   group('Transaction:Query recovery', () {
-    PostgreSQLConnection conn;
+    late PostgreSQLConnection conn;
 
     setUp(() async {
       conn = PostgreSQLConnection('localhost', 5432, 'dart_test',
@@ -305,7 +309,7 @@ void main() {
     });
 
     tearDown(() async {
-      await conn?.close();
+      await conn.close();
     });
 
     test('Is rolled back/executes later query', () async {
@@ -396,7 +400,7 @@ void main() {
   });
 
   group('Transaction:Exception recovery', () {
-    PostgreSQLConnection conn;
+    late PostgreSQLConnection conn;
 
     setUp(() async {
       conn = PostgreSQLConnection('localhost', 5432, 'dart_test',
@@ -406,7 +410,7 @@ void main() {
     });
 
     tearDown(() async {
-      await conn?.close();
+      await conn.close();
     });
 
     test('Is rolled back/executes later query', () async {
@@ -542,7 +546,7 @@ void main() {
   });
 
   group('Transaction:Rollback recovery', () {
-    PostgreSQLConnection conn;
+    late PostgreSQLConnection conn;
 
     setUp(() async {
       conn = PostgreSQLConnection('localhost', 5432, 'dart_test',
@@ -552,7 +556,7 @@ void main() {
     });
 
     tearDown(() async {
-      await conn?.close();
+      await conn.close();
     });
 
     test('Is rolled back/executes later query', () async {