context: use "canceled" in docs to refer to timed-out contexts

In documentation, we've usually but not always referred to a
context with a closed Done channel as "done" rather than
"canceled", to avoid ambiguity between a context canceled
by calling a CancelFunc and one past its deadline.

This actually adds ambiguity, however, since it's common to
see references to a "canceled context" that are intended to
cover contexts past their deadline. If you see "function F
returns if its context is canceled", you can reasonably
assume that F will return if its context passes its
deadline, unless something says otherwise.

Update the context package docs to explicitly state that
a context is canceled when its deadline passes. Drop references
to contexts becoming "done" and just use "canceled" throughout.

Fixes #70945

Change-Id: I99fbd800c6049deaa37015a304f7f9d9a84100e1
Reviewed-on: https://go-review.googlesource.com/c/go/+/640095
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Damien Neil <dneil@google.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/context/example_test.go b/src/context/example_test.go
index b597b09f16..be8cd8376e 100644
--- a/src/context/example_test.go
+++ b/src/context/example_test.go
@@ -146,8 +146,8 @@ func ExampleAfterFunc_cond() {
 		defer stopf()
 
 		// Since the wakeups are using Broadcast instead of Signal, this call to
-		// Wait may unblock due to some other goroutine's context becoming done,
-		// so to be sure that ctx is actually done we need to check it in a loop.
+		// Wait may unblock due to some other goroutine's context being canceled,
+		// so to be sure that ctx is actually canceled we need to check it in a loop.
 		for !conditionMet() {
 			cond.Wait()
 			if ctx.Err() != nil {