This is preparation to support Go module. Updates golang/go#27234 Change-Id: I8dcaed231e877e81d2072c7c85321c0acb6a8b1b Reviewed-on: https://go-review.googlesource.com/c/mobile/+/203397 Run-TryBot: Hajime Hoshi <hajimehoshi@gmail.com> Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com> TryBot-Result: Gobot Gobot <gobot@golang.org>