[release-branch.go1.8] testing: stop timeout-timer after running tests

Fixes #18845

Fixes #18870 (Go 1.8 backport)

Change-Id: Icdc3e2067807781e42f2ffc94d1824aed94d3713
Reviewed-on: https://go-review.googlesource.com/35956
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
(cherry picked from commit 7d8bfdde)
Reviewed-on: https://go-review.googlesource.com/36125

src/cmd/go/go_test.go

@@ -3744,6 +3744,13 @@ func TestMatchesOnlySubtestParallelIsOK(t *testing.T) {
 	tg.grepBoth(okPattern, "go test did not say ok")
 }
 
+// Issue 18845
+func TestBenchTimeout(t *testing.T) {
+	tg := testgo(t)
+	defer tg.cleanup()
+	tg.run("test", "-bench", ".", "-timeout", "750ms", "testdata/timeoutbench_test.go")
+}
+
 func TestLinkXImportPathEscape(t *testing.T) {
 	// golang.org/issue/16710
 	tg := testgo(t)

src/cmd/go/testdata/timeoutbench_test.go

+package timeoutbench_test
+
+import (
+	"testing"
+	"time"
+)
+
+func BenchmarkSleep1s(b *testing.B) {
+	time.Sleep(1 * time.Second)
+}

src/testing/testing.go

@@ -821,6 +821,7 @@ func (m *M) Run() int {
 	haveExamples = len(m.examples) > 0
 	testRan, testOk := runTests(m.deps.MatchString, m.tests)
 	exampleRan, exampleOk := runExamples(m.deps.MatchString, m.examples)
+	stopAlarm()
 	if !testRan && !exampleRan && *matchBenchmarks == "" {
 		fmt.Fprintln(os.Stderr, "testing: warning: no tests to run")
 	}