all: go fmt ./...

Make all our package sources use Go 1.17 gofmt format
(adding //go:build lines).

Not strictly necessary but will avoid spurious changes
as files are edited.

Part of //go:build change (#41184).
See https://golang.org/design/draft-gobuild

Change-Id: I22803ea9e936fbb08984a64155302f47e181de27
Reviewed-on: https://go-review.googlesource.com/c/oauth2/+/294420
Trust: Russ Cox <rsc@golang.org>
Trust: Cody Oss <codyoss@google.com>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cody Oss <codyoss@google.com>

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)
 }