Alter BuildQuery to handle map

params.go

@@ -1,6 +1,7 @@
 package gophercloud
 
 import (
+	"encoding/json"
 	"fmt"
 	"net/url"
 	"reflect"
@@ -155,6 +156,17 @@ func BuildQueryString(opts interface{}) (*url.URL, error) {
 								params.Add(tags[0], v.Index(i).String())
 							}
 						}
+					case reflect.Map:
+						vi := v.Interface()
+						mp, ok := vi.(map[string]string)
+						if !ok {
+							return nil, fmt.Errorf("Query opt [%v] is not type map[string]string, not supported.", v)
+						}
+						s, err := buildMapParam(mp)
+						if err != nil {
+							return nil, err
+						}
+						params.Add(tags[0], s)
 					}
 				} else {
 					// Otherwise, the field is not set.
@@ -172,6 +184,14 @@ func BuildQueryString(opts interface{}) (*url.URL, error) {
 	return nil, fmt.Errorf("Options type is not a struct.")
 }
 
+func buildMapParam(v map[string]string) (string, error) {
+	s, err := json.Marshal(v)
+	if err != nil {
+		return "", err
+	}
+	return string(s), nil
+}
+
 /*
 BuildHeaders is an internal function to be used by request methods in
 individual resource packages.

params_test.go

@@ -36,34 +36,37 @@ func TestMaybeInt(t *testing.T) {
 func TestBuildQueryString(t *testing.T) {
 	type testVar string
 	opts := struct {
-		J  int       `q:"j"`
-		R  string    `q:"r,required"`
-		C  bool      `q:"c"`
-		S  []string  `q:"s"`
-		TS []testVar `q:"ts"`
-		TI []int     `q:"ti"`
+		J  int               `q:"j"`
+		R  string            `q:"r,required"`
+		C  bool              `q:"c"`
+		S  []string          `q:"s"`
+		TS []testVar         `q:"ts"`
+		TI []int             `q:"ti"`
+		MP map[string]string `q:"mp"`
 	}{
 		J:  2,
 		R:  "red",
 		C:  true,
 		S:  []string{"one", "two", "three"},
 		TS: []testVar{"a", "b"},
 		TI: []int{1, 2},
+		MP: map[string]string{"k1": "v1", "k2": "v2"},
 	}
-	expected := &url.URL{RawQuery: "c=true&j=2&r=red&s=one&s=two&s=three&ti=1&ti=2&ts=a&ts=b"}
+	expected := &url.URL{RawQuery: "c=true&j=2&mp=%7B%22k1%22%3A%22v1%22%2C%22k2%22%3A%22v2%22%7D&r=red&s=one&s=two&s=three&ti=1&ti=2&ts=a&ts=b"}
 	actual, err := BuildQueryString(&opts)
 	if err != nil {
 		t.Errorf("Error building query string: %v", err)
 	}
 	th.CheckDeepEquals(t, expected, actual)
 
 	opts = struct {
-		J  int       `q:"j"`
-		R  string    `q:"r,required"`
-		C  bool      `q:"c"`
-		S  []string  `q:"s"`
-		TS []testVar `q:"ts"`
-		TI []int     `q:"ti"`
+		J  int               `q:"j"`
+		R  string            `q:"r,required"`
+		C  bool              `q:"c"`
+		S  []string          `q:"s"`
+		TS []testVar         `q:"ts"`
+		TI []int             `q:"ti"`
+		MP map[string]string `q:"mp"`
 	}{
 		J: 2,
 		C: true,