Add event interface to send ids in event responses

Author: beornf

Diff for: render.go

@@ -15,6 +15,11 @@ type Binder interface {
 	Bind(r *http.Request) error
 }
 
+// Event interface for event stream responses.
+type Event interface {
+	GetID() string
+}
+
 // Bind decodes a request body and executes the Binder method of the
 // payload structure.
 func Bind(r *http.Request, v Binder) error {

Diff for: responder.go

@@ -190,7 +190,15 @@ func channelEventStream(w http.ResponseWriter, r *http.Request, v interface{}) {
 				}
 				continue
 			}
-			w.Write([]byte(fmt.Sprintf("event: data\ndata: %s\n\n", bytes)))
+			var resp string
+			if ev, ok := v.(Event); ok {
+				id := ev.GetID()
+				if id != "" {
+					resp += fmt.Sprintf("id: %s\n", id)
+				}
+			}
+			resp += fmt.Sprintf("event: data\ndata: %s\n\n", bytes)
+			w.Write([]byte(resp))
 			if f, ok := w.(http.Flusher); ok {
 				f.Flush()
 			}