log: avoid leaking goroutines in TestOutputRace

Leaked goroutines are the only explanation I can think of for excess
allocs in TestDiscard, and TestOutputRace is the only place I can see
where the log package leaks goroutines. Let's fix that leak and see if
it eliminates the TestDiscard flakes.

Fixes #58797 (maybe).

Change-Id: I2d54dcba3eb52bd10a62cd1c380131add6a2f651
Reviewed-on: https://go-review.googlesource.com/c/go/+/487356
TryBot-Result: Gopher Robot <[email protected]>
Auto-Submit: Bryan Mills <[email protected]>
Run-TryBot: Bryan Mills <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>

Author: Bryan C. Mills

src/log/log_test.go

@@ -109,12 +109,16 @@ func TestNonNewLogger(t *testing.T) {
 func TestOutputRace(t *testing.T) {
 	var b bytes.Buffer
 	l := New(&b, "", 0)
+	var wg sync.WaitGroup
+	wg.Add(100)
 	for i := 0; i < 100; i++ {
 		go func() {
+			defer wg.Done()
 			l.SetFlags(0)
 			l.Output(0, "")
 		}()
 	}
+	wg.Wait()
 }
 
 func TestFlagAndPrefixSetting(t *testing.T) {