Merge pull request #98 from wework/fixdoc

Adding and fixing documentation issues

Author: Guy Baron

README.md

@@ -20,13 +20,14 @@ A lightweight transactional message bus on top of RabbitMQ supporting:
 4) Publisher confirms
 5) [Reliable messaging](https://github.com/wework/grabbit/blob/master/docs/OUTBOX.md) and local service transactivity via Transaction Outbox pattern
 6) Deadlettering
+7) [Structured logging](https://github.com/wework/grabbit/blob/master/docs/LOGGING.md)
 
 Planned:
 
 1) Deduplication of inbound messages
 
 ## Stable release
-the v1.x branch contains the latest stable releases of grabbit and one should track that branch to get point and minor release updates. 
+the v1.x branch contains the latest stable releases of grabbit and one should track that branch to get point and minor release updates.
 
 ## Supported transactional resources
 1) MySql > 8.0 (InnoDB)
@@ -78,8 +79,8 @@ Register a command handler
 ```Go
 
 
-handler := func(invocation gbus.Invocation, message *gbus.BusMessage) error
-    cmd, ok := message.Payload.(SomeCommand)
+handler := func(invocation gbus.Invocation, message *gbus.BusMessage) error{
+    cmd, ok := message.Payload.(*SomeCommand)
     if ok {
       fmt.Printf("handler invoked with  message %v", cmd)
             return nil
@@ -96,7 +97,7 @@ Register an event handler
 
 
 eventHandler := func(invocation gbus.Invocation, message *gbus.BusMessage) {
-    evt, ok := message.Payload.(SomeEvent)
+    evt, ok := message.Payload.(*SomeEvent)
     if ok {
       fmt.Printf("handler invoked with event %v", evt)
             return nil

docs/LOGGING.md

@@ -0,0 +1,22 @@
+# Logging
+
+grabbit supports structured logging via the [logrus](https://github.com/sirupsen/logrus) logging package.
+The logger is accessible to message handlers via the past in invocation instance.
+
+```go
+
+func SomeHandler(invocation gbus.Invocation, message *gbus.BusMessage) error{
+    invocation.Log().WithField("name", "rhinof").Info("handler invoked")
+    return nil
+  }
+
+```
+
+grabbit will create a default instance of logrus FieldLogger if no such logger is set when the bus is created.
+In order to set a custom logger when creating the bus you need to call the Builder.WithLogger method passing it
+a logrus.FieldLogger instance.
+
+```go
+
+
+```