Per comments in https://github.com/golang/go/issues/20239#issuecomment-402199944

Updates #20239
Updates #26303

Change-Id: Iddf34c0452bd30ca9111b951bca48d1e011bd85a
Reviewed-on: https://go-review.googlesource.com/122820
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>