Add Context cancellation to clock.

appengine/memlock/memlock.go

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Package memlock allows multiple appengine handlers to coordinate best-effort
 // mutual execution via memcache. "best-effort" here means "best-effort"...
 // memcache is not reliable. However, colliding on memcache is a lot cheaper
 // than, for example, colliding with datastore transactions.
 package memlock
 
@@ skipping 134 matching lines @@
         testStopCB, _ := ctx.Value(testStopCBKey).(func())
 
         // This goroutine checks to see if we still posess the lock, and refreshes it
         // if we do.
         go func() {
                 defer func() {
                         cancelFunc()
                         close(finished)
                 }()
 
-        checkLoop:
                 for {
-                        select {
-                        case <-subCtx.Done():
-                                break checkLoop
-                        case <-clock.Get(ctx).After(delay):
+                        if (<-clock.After(subCtx, delay)).Err != nil {

[dnj (Google), 2016/02/10 03:40:08]

Nice, eh?

+                                break
                         }
                         if !checkAnd(refresh) {
                                 log.Warningf("lost lock: %s", err)
                                 return
                         }
                 }
 
                 if testStopCB != nil {
                         testStopCB()
                 }
                 checkAnd(release)
         }()
 
         return f(subCtx)
 }