cmd/go: respect test -timeout flag

I thought that -timeout was per-test, but it is for the
whole program execution, so cmd/go can adjust its timer
(also for whole program execution) accordingly.

Fixes #2993.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5650070

src/cmd/go/test.go

@@ -198,10 +198,13 @@ var (
 	testX            bool     // -x flag
 	testV            bool     // -v flag
 	testFiles        []string // -file flag(s)  TODO: not respected
+	testTimeout      string   // -timeout flag
 	testArgs         []string
 	testBench        bool
 	testStreamOutput bool // show output as it is generated
 	testShowPass     bool // show passing output
+
+	testKillTimeout = 10 * time.Minute
 )
 
 func runTest(cmd *Command, args []string) {
@@ -217,6 +220,14 @@ func runTest(cmd *Command, args []string) {
 		fatalf("cannot use -c flag with multiple packages")
 	}
 
+	// If a test timeout was given and is parseable, set our kill timeout
+	// to that timeout plus one minute.  This is a backup alarm in case
+	// the test wedges with a goroutine spinning and its background
+	// timer does not get a chance to fire.
+	if dt, err := time.ParseDuration(testTimeout); err == nil {
+		testKillTimeout = dt + 1*time.Minute
+	}
+
 	// show passing test output (after buffering) with -v flag.
 	// must buffer because tests are running in parallel, and
 	// otherwise the output will get mixed.
@@ -540,9 +551,7 @@ func (b *builder) runTest(a *action) error {
 	// This is a last-ditch deadline to detect and
 	// stop wedged test binaries, to keep the builders
 	// running.
-	const deadline = 10 * time.Minute
-
-	tick := time.NewTimer(deadline)
+	tick := time.NewTimer(testKillTimeout)
 	if err == nil {
 		done := make(chan error)
 		go func() {

src/cmd/go/testflag.go

@@ -133,6 +133,8 @@ func testFlags(args []string) (packageNames, passToTest []string) {
 		case "bench":
 			// record that we saw the flag; don't care about the value
 			testBench = true
+		case "timeout":
+			testTimeout = value
 		}
 		if extraWord {
 			i++