From 42a4f6f9cbefb56698b9a4274473020188031754 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B8rn=20Erik=20Pedersen?=
 <bjorn.erik.pedersen@gmail.com>
Date: Fri, 31 Mar 2017 10:40:33 +0200
Subject: [PATCH] tplimpl: Fix map data race in URLLock

---
 tpl/tplimpl/template_resources.go | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/tpl/tplimpl/template_resources.go b/tpl/tplimpl/template_resources.go
index f10aa72e3..cfec816ad 100644
--- a/tpl/tplimpl/template_resources.go
+++ b/tpl/tplimpl/template_resources.go
@@ -46,12 +46,17 @@ type remoteLock struct {
 
 // URLLock locks an URL during download
 func (l *remoteLock) URLLock(url string) {
+	var (
+		lock *sync.Mutex
+		ok   bool
+	)
 	l.Lock()
-	if _, ok := l.m[url]; !ok {
-		l.m[url] = &sync.Mutex{}
+	if lock, ok = l.m[url]; !ok {
+		lock = &sync.Mutex{}
+		l.m[url] = lock
 	}
 	l.Unlock()
-	l.m[url].Lock()
+	lock.Lock()
 }
 
 // URLUnlock unlocks an URL when the download has been finished. Use only in defer calls.