Merge pull request #67359 from mikedanese/reloadtoken

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions here: https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md.

client: periodically reload InClusterConfig token

/sig auth
/sig api-machinery

```release-note
NONE
```

Kubernetes-commit: 7b6647a418c660f2c87f183f706b297f1cb573ca

vendor/golang.org/x/oauth2/client_appengine.go

@@ -0,0 +1,25 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build appengine
+
+// App Engine hooks.
+
+package oauth2
+
+import (
+	"net/http"
+
+	"golang.org/x/net/context"
+	"golang.org/x/oauth2/internal"
+	"google.golang.org/appengine/urlfetch"
+)
+
+func init() {
+	internal.RegisterContextClientFunc(contextClientAppEngine)
+}
+
+func contextClientAppEngine(ctx context.Context) (*http.Client, error) {
+	return urlfetch.Client(ctx), nil
+}