Updates golang/go#17790

Change-Id: I7bc596d9a80490d545ad3d1de5859efce34714f6
Reviewed-on: https://go-review.googlesource.com/33102
TryBot-Result: Gobot Gobot <gobot@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>