[release-branch.go1.16] cmd/go: fix mod_get_direct
https://github.com/googleapis/google-cloud-go has changed the default
branch from master to main, causing mod_get_direct failed on longtest.
Change-Id: I8fe0356b2ff532d1fdedbcb1e1832d7335babaa0
Reviewed-on: https://go-review.googlesource.com/c/go/+/361965
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
(cherry picked from commit
b7529c3617a64ed5d1e2a6c7a9366d4a4988a38d)
Reviewed-on: https://go-review.googlesource.com/c/go/+/362536
Trust: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>