go/printer: simplify test

Pre Go1?

LGTM=r
R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/115870043

src/pkg/go/printer/printer_test.go

@@ -159,13 +159,6 @@ func runcheck(t *testing.T, source, golden string, mode checkMode) {
 }
 
 func check(t *testing.T, source, golden string, mode checkMode) {
-	// start a timer to produce a time-out signal
-	tc := make(chan int)
-	go func() {
-		time.Sleep(10 * time.Second) // plenty of a safety margin, even for very slow machines
-		tc <- 0
-	}()
-
 	// run the test
 	cc := make(chan int)
 	go func() {
@@ -173,9 +166,9 @@ func check(t *testing.T, source, golden string, mode checkMode) {
 		cc <- 0
 	}()
 
-	// wait for the first finisher
+	// wait with timeout
 	select {
-	case <-tc:
+	case <-time.After(10 * time.Second): // plenty of a safety margin, even for very slow machines
 		// test running past time out
 		t.Errorf("%s: running too slowly", source)
 	case <-cc: