From 758ce9c3fbb23aba35e454d7444fb1c909b58341 Mon Sep 17 00:00:00 2001
From: Justin Powell <powelles@users.noreply.github.com>
Date: Tue, 25 Oct 2016 11:41:40 -0700
Subject: [PATCH] Add mutex to prevent concurrent connection write

---
 examples/chat/client.go | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/examples/chat/client.go b/examples/chat/client.go
index c3c518d..25a664a 100644
--- a/examples/chat/client.go
+++ b/examples/chat/client.go
@@ -8,6 +8,7 @@ import (
 	"bytes"
 	"log"
 	"net/http"
+	"sync"
 	"time"
 
 	"github.com/gorilla/websocket"
@@ -46,6 +47,9 @@ type Client struct {
 
 	// Buffered channel of outbound messages.
 	send chan []byte
+	
+	// Mutex to prevent concurrent connection write.
+	mux sync.Mutex
 }
 
 // readPump pumps messages from the websocket connection to the hub.
@@ -72,6 +76,8 @@ func (c *Client) readPump() {
 
 // write writes a message with the given message type and payload.
 func (c *Client) write(mt int, payload []byte) error {
+	c.mux.Lock()
+	defer c.mux.Unlock()
 	c.conn.SetWriteDeadline(time.Now().Add(writeWait))
 	return c.conn.WriteMessage(mt, payload)
 }