This CL fixes TestDocs to test with Go modules by packagestest. Updates golang/go#27234 Change-Id: I9055f52d26e494cd3b71b59d3db0755d415df356 Reviewed-on: https://go-review.googlesource.com/c/mobile/+/206737 Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>