use variadics and fix build tags for App Engine files

google/appengine.go

@@ -2,8 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build appengine
-// +build !appenginevm
+// +build appengine,!appenginevm
 
 package google
 
@@ -30,7 +29,7 @@ type AppEngineConfig struct {
 
 // NewAppEngineConfig creates a new AppEngineConfig for the
 // provided auth scopes.
-func NewAppEngineConfig(context appengine.Context, scopes []string) *AppEngineConfig {
+func NewAppEngineConfig(context appengine.Context, scopes ...string) *AppEngineConfig {
 	return &AppEngineConfig{
 		context: context,
 		scopes:  scopes,

google/appenginevm.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build appenginevm
+// +build appenginevm !appengine
 
 package google
 
@@ -27,7 +27,7 @@ type AppEngineConfig struct {
 
 // NewAppEngineConfig creates a new AppEngineConfig for the
 // provided auth scopes.
-func NewAppEngineConfig(context appengine.Context, scopes []string) *AppEngineConfig {
+func NewAppEngineConfig(context appengine.Context, scopes ...string) *AppEngineConfig {
 	return &AppEngineConfig{
 		context: context,
 		scopes:  scopes,

google/example_test.go

@@ -112,10 +112,8 @@ func Example_serviceAccounts() {
 }
 
 func Example_appEngine() {
-	context := appengine.NewContext(nil)
-	config := google.NewAppEngineConfig(context, []string{
-		"https://www.googleapis.com/auth/bigquery",
-	})
+	c := appengine.NewContext(nil)
+	config := google.NewAppEngineConfig(c, "https://www.googleapis.com/auth/bigquery")
 	// The following client will be authorized by the App Engine
 	// app's service account for the provided scopes.
 	client := http.Client{Transport: config.NewTransport()}