Websocket client & server

client.js

const url = 'ws://localhost:1234'
let ws = new WebSocket(url,'test_protocol') 
ws.onopen = () => {
  console.log('Client connection opened')
  ws.send('Hello Websocket')
}

ws.onmessage = (event) => {
  console.log('Received message : '+ event.data)
}
ws.onclose = () => {
  console.log('Close ws')
}
ws.onerror = (event) => {
  console.log('Error : ', event)
  ws.close()
}

server.go

package main

import (
	"net/http"
	"time"

	"github.com/gorilla/websocket"
	logging "github.com/op/go-logging"
)

var upgrader *websocket.Upgrader
var logger *logging.Logger

func init() {
	logger = logging.MustGetLogger("main")
	logging.SetLevel(logging.INFO, "main")
	upgrader = &websocket.Upgrader{
		HandshakeTimeout: 5 * time.Second,
		Subprotocols:     []string{"test_protocol"},
		CheckOrigin: func(r *http.Request) bool {
			return true
		},
	}
}
func websocketHandler(w http.ResponseWriter, r *http.Request) {
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		logger.Errorf("Websocket upgrade err : %s", err.Error())
		return
	}
	defer func(conn *websocket.Conn) {
		err := conn.Close()
		if err != nil {
			logger.Errorf("Error closing websocket connection : %s", err.Error())
		}
		logger.Info("Connection closed")
	}(conn)

	for {
		messageType, message, err := conn.ReadMessage()
		if err != nil {
			logger.Errorf("Error reading messages from client : %s", err.Error())
			break
		}
		logger.Infof("Received message : %s", string(message[:]))
		err = conn.WriteMessage(messageType, []byte("Websocket server"))
		if err != nil {
			logger.Errorf("Error writing messages : %s", err.Error())
			break
		}
		logger.Info("Send message : Websocket server")
		if string(message[:]) == "close ws" {
			break
		}
	}
}
func main() {
	http.HandleFunc("/", websocketHandler)
	logger.Fatal(http.ListenAndServe(":1234", nil))
}