From 355736ec357c81dfb2eb6851ee019d407090c5ec Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B8rn=20Erik=20Pedersen?=
 <bjorn.erik.pedersen@gmail.com>
Date: Sun, 30 Apr 2017 01:10:03 +0200
Subject: [PATCH] livereload: Fix data race in close

Fixes #2625
---
 livereload/connection.go | 11 +++++++++++
 livereload/hub.go        |  4 ++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/livereload/connection.go b/livereload/connection.go
index 6e31b1baf..4e94e2ee0 100644
--- a/livereload/connection.go
+++ b/livereload/connection.go
@@ -15,6 +15,7 @@ package livereload
 
 import (
 	"bytes"
+	"sync"
 
 	"github.com/gorilla/websocket"
 )
@@ -25,6 +26,16 @@ type connection struct {
 
 	// Buffered channel of outbound messages.
 	send chan []byte
+
+	// There is a potential data race, especially visible with large files.
+	// This is protected by synchronisation of the send channel's close.
+	closer sync.Once
+}
+
+func (c *connection) close() {
+	c.closer.Do(func() {
+		close(c.send)
+	})
 }
 
 func (c *connection) reader() {
diff --git a/livereload/hub.go b/livereload/hub.go
index 359bac3f1..8ab6083ad 100644
--- a/livereload/hub.go
+++ b/livereload/hub.go
@@ -41,14 +41,14 @@ func (h *hub) run() {
 			h.connections[c] = true
 		case c := <-h.unregister:
 			delete(h.connections, c)
-			close(c.send)
+			c.close()
 		case m := <-h.broadcast:
 			for c := range h.connections {
 				select {
 				case c.send <- m:
 				default:
 					delete(h.connections, c)
-					close(c.send)
+					c.close()
 				}
 			}
 		}