Only support single signature for subscriber and validate

examples/server/main.go

@@ -39,19 +39,23 @@ func main() {
 	)
 
 	// Register Subscribers
-	server.Subscribe(
+	if err := server.Subscribe(
 		server.NewSubscriber(
 			"topic.go.micro.srv.example",
 			new(subscriber.Example),
 		),
-	)
+	); err != nil {
+		log.Fatal(err)
+	}
 
-	server.Subscribe(
+	if err := server.Subscribe(
 		server.NewSubscriber(
 			"topic.go.micro.srv.example",
 			subscriber.Handler,
 		),
-	)
+	); err != nil {
+		log.Fatal(err)
+	}
 
 	// Run server
 	if err := server.Run(); err != nil {

examples/server/subscriber/subscriber.go

@@ -13,6 +13,7 @@ func (e *Example) Handle(ctx context.Context, msg *example.Message) error {
 	return nil
 }
 
-func Handler(msg *example.Message) {
+func Handler(ctx context.Context, msg *example.Message) error {
 	log.Info("Function Received message: ", msg.Say)
+	return nil
 }