cmd/go: modload should use a read-write lock to improve concurrency
This PR will be imported into Gerrit with the title and first
comment (this text) used to generate the subject and body of
the Gerrit change.
Change-Id: I3f9bc8a2459059a924a04fa02794e258957819b5
GitHub-Last-Rev:
6ad6f6a70e21dc45fc0c880b8732fb87c656c520
GitHub-Pull-Request: golang/go#74311
Reviewed-on: https://go-review.googlesource.com/c/go/+/683215
Reviewed-by: Michael Matloob <matloob@golang.org>
Reviewed-by: Ian Alexander <jitsu@google.com>
Reviewed-by: Michael Matloob <matloob@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>