test/fixedbugs: bump issue21576.go's timeout to 1min

Increases the exec timeout from 5sec to 1min, but
also print out the error value on any test failure.

Fixes #34836

Change-Id: Ida2b8bd460243491ef0f90dfe0f978dfe02a0703
Reviewed-on: https://go-review.googlesource.com/c/go/+/200519
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

test/fixedbugs/issue21576.go

@@ -44,7 +44,9 @@ func main() {
 		log.Fatalf("Write error %v", err)
 	}
 
-	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	// Using a timeout of 1 minute in case other factors might slow
+	// down the start of "go run". See https://golang.org/issue/34836.
+	ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
 	defer cancel()
 
 	cmd := exec.CommandContext(ctx, "go", "run", file)
@@ -55,6 +57,6 @@ func main() {
 
 	want := []byte("fatal error: all goroutines are asleep - deadlock!")
 	if !bytes.Contains(output, want) {
-		log.Fatalf("Unmatched error message %q:\nin\n%s", want, output)
+		log.Fatalf("Unmatched error message %q:\nin\n%s\nError: %v", want, output, err)
 	}
 }