context: make DeadlineExceeded have a Timeout method

Fixes #14238

Change-Id: I1538bfb5cfa63e36a89df1f6eb9f5a0dcafb6ce5
Reviewed-on: https://go-review.googlesource.com/23256
Reviewed-by: Dave Cheney <dave@cheney.net>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/context/context_test.go b/src/context/context_test.go
index 99456b188d..90e78e57ec 100644
--- a/src/context/context_test.go
+++ b/src/context/context_test.go
@@ -594,3 +594,15 @@ func recoveredValue(fn func()) (v interface{}) {
 	fn()
 	return
 }
+
+func TestDeadlineExceededSupportsTimeout(t *testing.T) {
+	i, ok := DeadlineExceeded.(interface {
+		Timeout() bool
+	})
+	if !ok {
+		t.Fatal("DeadlineExceeded does not support Timeout interface")
+	}
+	if !i.Timeout() {
+		t.Fatal("wrong value for timeout")
+	}
+}