net: support context cancellation in acquireThread
acquireThread is already waiting on a channel, so
it can be easily wired up to support context cancellation.
This change will make sure that contexts that are
cancelled at the acquireThread stage (when the limit of
threads is reached) do not queue unnecessarily and cause
an unnecessary cgo call that will be soon aborted by
the doBlockingWithCtx function.
Updates #63978
Change-Id: I8ae4debd51995637567d8f51c6f1ed60f23d6c0c
GitHub-Last-Rev:
4189b9faf07c073a2ca440becee07b6aa9c4e795
GitHub-Pull-Request: golang/go#63985
Reviewed-on: https://go-review.googlesource.com/c/go/+/539360
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Commit-Queue: Ian Lance Taylor <iant@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>