Updates golang/go#14974

Change-Id: I80da378a788d5d826b3b79ab308372231c012391
Reviewed-on: https://go-review.googlesource.com/23105Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com>
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>