context: update doc comment to link to context interface
Linking to the Context interface in the WithCancel doc comment makes
it more consistent with the WithDeadline and WithTimeout doc comments.
Change-Id: Ic935c63e8262784be5f3564816402221ba2fbd63
GitHub-Last-Rev:
9c6bb607a94f6f4cd27cc3f5e39c192e088ab386
GitHub-Pull-Request: golang/go#65768
Reviewed-on: https://go-review.googlesource.com/c/go/+/564996
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>