Data Race when SetReportCaller is true

[georlav]

func TestSetReportCallerRace(t *testing.T) {
	l := New()
	l.Out = ioutil.Discard
	l.SetReportCaller(true)

	var wg sync.WaitGroup
	wg.Add(100)

	for i := 0; i < 100; i++ {
		go func() {
			l.Error("Some Error")
			wg.Done()
		}()
	}

	wg.Wait()
}

WARNING: DATA RACE
Read at 0x000000c75b98 by goroutine 14:
github.com/sirupsen/logrus.getCaller()
/home/georlav/other/logrus/entry.go:161 +0x7b
github.com/sirupsen/logrus.Entry.log()
/home/georlav/other/logrus/entry.go:210 +0x395
github.com/sirupsen/logrus.(*Entry).Log()
/home/georlav/other/logrus/entry.go:258 +0x154
github.com/sirupsen/logrus.(*Logger).Log()
/home/georlav/other/logrus/logger.go:184 +0xa4
github.com/sirupsen/logrus_test.TestSetReportCallerRace.func1()
/home/georlav/other/logrus/logger.go:216 +0x81

Previous write at 0x000000c75b98 by goroutine 7:
github.com/sirupsen/logrus.getCaller.func1()
/home/georlav/other/logrus/entry.go:170 +0xe1
sync.(*Once).Do()
/snap/go/3318/src/sync/once.go:44 +0xde
github.com/sirupsen/logrus.getCaller()
/home/georlav/other/logrus/entry.go:165 +0x149
github.com/sirupsen/logrus.Entry.log()
/home/georlav/other/logrus/entry.go:210 +0x395
github.com/sirupsen/logrus.(*Entry).Log()
/home/georlav/other/logrus/entry.go:258 +0x154
github.com/sirupsen/logrus.(*Logger).Log()
/home/georlav/other/logrus/logger.go:184 +0xa4
github.com/sirupsen/logrus_test.TestSetReportCallerRace.func1()
/home/georlav/other/logrus/logger.go:216 +0x81