Add a gRPC router wrapper, useful for the upcoming grpc controller example

Former-commit-id: ae4c29597ce1336a74278b86b59d08b6c91eab0a

_examples/websocket/socketio/main.go

@@ -52,3 +52,8 @@ func main() {
 		iris.WithoutServerError(iris.ErrServerClosed),
 	)
 }
+
+/*
+If you want to enable CORS in your websocket handler,
+please follow this post: https://github.com/googollee/go-socket.io/issues/242
+*/