diff --git a/google/appengine_gen1.go b/google/appengine_gen1.go
index 83dacac..16c6c6b 100644
--- a/google/appengine_gen1.go
+++ b/google/appengine_gen1.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build appengine
 // +build appengine
 
 // This file applies to App Engine first generation runtimes (<= Go 1.9).
diff --git a/google/appengine_gen2_flex.go b/google/appengine_gen2_flex.go
index 04c2c22..a7e27b3 100644
--- a/google/appengine_gen2_flex.go
+++ b/google/appengine_gen2_flex.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !appengine
 // +build !appengine
 
 // This file applies to App Engine second generation runtimes (>= Go 1.11) and App Engine flexible.
diff --git a/google/internal/externalaccount/basecredentials.go b/google/internal/externalaccount/basecredentials.go
index d0ca23c..1b87c09 100644
--- a/google/internal/externalaccount/basecredentials.go
+++ b/google/internal/externalaccount/basecredentials.go
@@ -45,7 +45,7 @@ func (c *Config) TokenSource(ctx context.Context) oauth2.TokenSource {
 		ctx:    ctx,
 		url:    c.ServiceAccountImpersonationURL,
 		scopes: scopes,
-		ts: oauth2.ReuseTokenSource(nil, ts),
+		ts:     oauth2.ReuseTokenSource(nil, ts),
 	}
 	return oauth2.ReuseTokenSource(nil, imp)
 }
diff --git a/google/internal/externalaccount/urlcredsource_test.go b/google/internal/externalaccount/urlcredsource_test.go
index 6874f11..8ade2a2 100644
--- a/google/internal/externalaccount/urlcredsource_test.go
+++ b/google/internal/externalaccount/urlcredsource_test.go
@@ -29,8 +29,8 @@ func TestRetrieveURLSubjectToken_Text(t *testing.T) {
 	heads := make(map[string]string)
 	heads["Metadata"] = "True"
 	cs := CredentialSource{
-		URL:    ts.URL,
-		Format: format{Type: fileTypeText},
+		URL:     ts.URL,
+		Format:  format{Type: fileTypeText},
 		Headers: heads,
 	}
 	tfc := testFileConfig
diff --git a/internal/client_appengine.go b/internal/client_appengine.go
index 7434871..e1755d1 100644
--- a/internal/client_appengine.go
+++ b/internal/client_appengine.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build appengine
 // +build appengine
 
 package internal