cmd/dist: increase default cmd/go test timeout

cmd/go has grown slow, even in short mode, and it's now regularly
failing on a number of builders where it's taking over the previous 3
minute timeout. for now, give it more time.

Change-Id: If565baf71c2770880b2e2139b47e03433951331f
Reviewed-on: https://go-review.googlesource.com/84235Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/dist/test.go

@@ -265,6 +265,10 @@ func (t *tester) registerStdTest(pkg string) {
 	if t.runRx == nil || t.runRx.MatchString(testName) == t.runRxWant {
 		stdMatches = append(stdMatches, pkg)
 	}
+	timeoutSec := 180
+	if pkg == "cmd/go" {
+		timeoutSec *= 2
+	}
 	t.tests = append(t.tests, distTest{
 		name:    testName,
 		heading: "Testing packages.",
@@ -280,7 +284,7 @@ func (t *tester) registerStdTest(pkg string) {
 				"test",
 				"-short",
 				t.tags(),
-				t.timeout(180),
+				t.timeout(timeoutSec),
 				"-gcflags=all=" + gogcflags,
 			}
 			if t.race {