support for parent-child relationship

goes.go

@@ -309,6 +309,10 @@ func (c *Connection) Get(index string, documentType string, id string, extraArgs
 // The extraArgs is a list of url.Values that you can send to elasticsearch as
 // URL arguments, for example, to control routing, ttl, version, op_type, etc.
 func (c *Connection) Index(d Document, extraArgs url.Values) (*Response, error) {
+	if parent, ok := d.Parent.(string); ok {
+		extraArgs.Set("parent", parent)
+	}
+
 	r := Request{
 		Conn:      c,
 		Query:     d.Fields,

goes_test.go

@@ -1424,3 +1424,59 @@ func (s *GoesTestSuite) TestAliasExists(c *C) {
 	exists, err = conn.AliasExists(alias)
 	c.Assert(exists, Equals, true)
 }
+
+func (s *GoesTestSuite) TestIndexWithChild(c *C) {
+	indexName := "testindexwithchild"
+	docType := "tweet"
+
+	conn := NewConnection(ES_HOST, ES_PORT)
+	// just in case
+	conn.DeleteIndex(indexName)
+
+	_, err := conn.CreateIndex(indexName, map[string]interface{}{})
+	c.Assert(err, IsNil)
+	//defer conn.DeleteIndex(indexName)
+
+	authorDoc := Document{
+		Index: indexName,
+		Type:  "author",
+		Fields: map[string]interface{}{
+			"name": "An Author",
+		},
+		Id: "aut",
+	}
+	response, err := conn.Index(authorDoc, url.Values{})
+	c.Assert(err, IsNil)
+
+	mapping := map[string]interface{}{
+		"tweet": map[string]interface{}{
+			"properties": map[string]interface{}{
+				"count": map[string]interface{}{
+					"type":  "integer",
+					"index": "not_analyzed",
+					"store": true,
+				},
+			},
+			"_parent": map[string]interface{}{
+				"type": "author",
+			},
+		},
+	}
+	response, err = conn.PutMapping("tweet", mapping, []string{indexName})
+	c.Assert(err, IsNil)
+
+	c.Assert(response.Acknowledged, Equals, true)
+	c.Assert(response.TimedOut, Equals, false)
+
+	d := Document{
+		Index: indexName,
+		Type:  docType,
+		Fields: map[string]interface{}{
+			"count": 5,
+		},
+		Parent: "aut",
+	}
+
+	response, err = conn.Index(d, url.Values{})
+	c.Assert(err, IsNil)
+}

structs.go

@@ -107,6 +107,7 @@ type Document struct {
 	Id          interface{}
 	BulkCommand string
 	Fields      interface{}
+	Parent      interface{}
 }
 
 // Represents the "items" field in a _bulk response