package logrus_test import ( "bytes" "encoding/json" "fmt" "io/ioutil" "os" "path/filepath" "runtime" "sync" "testing" "time" "github.com/stretchr/testify/assert" "github.com/stretchr/testify/require" . "github.com/sirupsen/logrus" . "github.com/sirupsen/logrus/internal/testutils" ) // TestReportCaller verifies that when ReportCaller is set, the 'func' field // is added, and when it is unset it is not set or modified // Verify that functions within the Logrus package aren't considered when // discovering the caller. func TestReportCallerWhenConfigured(t *testing.T) { LogAndAssertJSON(t, func(log *Logger) { log.ReportCaller = false log.Print("testNoCaller") }, func(fields Fields) { assert.Equal(t, "testNoCaller", fields["msg"]) assert.Equal(t, "info", fields["level"]) assert.Equal(t, nil, fields["func"]) }) LogAndAssertJSON(t, func(log *Logger) { log.ReportCaller = true log.Print("testWithCaller") }, func(fields Fields) { assert.Equal(t, "testWithCaller", fields["msg"]) assert.Equal(t, "info", fields["level"]) assert.Equal(t, "github.com/sirupsen/logrus_test.TestReportCallerWhenConfigured.func3", fields[FieldKeyFunc]) }) LogAndAssertJSON(t, func(log *Logger) { log.ReportCaller = true log.Formatter.(*JSONFormatter).CallerPrettyfier = func(f *runtime.Frame) (string, string) { return "somekindoffunc", "thisisafilename" } log.Print("testWithCallerPrettyfier") }, func(fields Fields) { assert.Equal(t, "somekindoffunc", fields[FieldKeyFunc]) assert.Equal(t, "thisisafilename", fields[FieldKeyFile]) }) LogAndAssertText(t, func(log *Logger) { log.ReportCaller = true log.Formatter.(*TextFormatter).CallerPrettyfier = func(f *runtime.Frame) (string, string) { return "somekindoffunc", "thisisafilename" } log.Print("testWithCallerPrettyfier") }, func(fields map[string]string) { assert.Equal(t, "somekindoffunc", fields[FieldKeyFunc]) assert.Equal(t, "thisisafilename", fields[FieldKeyFile]) }) } func logSomething(t *testing.T, message string) Fields { var buffer bytes.Buffer var fields Fields logger := New() logger.Out = &buffer logger.Formatter = new(JSONFormatter) logger.ReportCaller = true entry := logger.WithFields(Fields{ "foo": "bar", }) entry.Info(message) err := json.Unmarshal(buffer.Bytes(), &fields) assert.Nil(t, err) return fields } // TestReportCallerHelperDirect - verify reference when logging from a regular function func TestReportCallerHelperDirect(t *testing.T) { fields := logSomething(t, "direct") assert.Equal(t, "direct", fields["msg"]) assert.Equal(t, "info", fields["level"]) assert.Regexp(t, "github.com/.*/logrus_test.logSomething", fields["func"]) } // TestReportCallerHelperDirect - verify reference when logging from a function called via pointer func TestReportCallerHelperViaPointer(t *testing.T) { fptr := logSomething fields := fptr(t, "via pointer") assert.Equal(t, "via pointer", fields["msg"]) assert.Equal(t, "info", fields["level"]) assert.Regexp(t, "github.com/.*/logrus_test.logSomething", fields["func"]) } func TestPrint(t *testing.T) { LogAndAssertJSON(t, func(log *Logger) { log.Print("test") }, func(fields Fields) { assert.Equal(t, "test", fields["msg"]) assert.Equal(t, "info", fields["level"]) }) } func TestInfo(t *testing.T) { LogAndAssertJSON(t, func(log *Logger) { log.Info("test") }, func(fields Fields) { assert.Equal(t, "test", fields["msg"]) assert.Equal(t, "info", fields["level"]) }) } func TestWarn(t *testing.T) { LogAndAssertJSON(t, func(log *Logger) { log.Warn("test") }, func(fields Fields) { assert.Equal(t, "test", fields["msg"]) assert.Equal(t, "warning", fields["level"]) }) } func TestLog(t *testing.T) { LogAndAssertJSON(t, func(log *Logger) { log.Log(WarnLevel, "test") }, func(fields Fields) { assert.Equal(t, "test", fields["msg"]) assert.Equal(t, "warning", fields["level"]) }) } func TestInfolnShouldAddSpacesBetweenStrings(t *testing.T) { LogAndAssertJSON(t, func(log *Logger) { log.Infoln("test", "test") }, func(fields Fields) { assert.Equal(t, "test test", fields["msg"]) }) } func TestInfolnShouldAddSpacesBetweenStringAndNonstring(t *testing.T) { LogAndAssertJSON(t, func(log *Logger) { log.Infoln("test", 10) }, func(fields Fields) { assert.Equal(t, "test 10", fields["msg"]) }) } func TestInfolnShouldAddSpacesBetweenTwoNonStrings(t *testing.T) { LogAndAssertJSON(t, func(log *Logger) { log.Infoln(10, 10) }, func(fields Fields) { assert.Equal(t, "10 10", fields["msg"]) }) } func TestInfoShouldAddSpacesBetweenTwoNonStrings(t *testing.T) { LogAndAssertJSON(t, func(log *Logger) { log.Infoln(10, 10) }, func(fields Fields) { assert.Equal(t, "10 10", fields["msg"]) }) } func TestInfoShouldNotAddSpacesBetweenStringAndNonstring(t *testing.T) { LogAndAssertJSON(t, func(log *Logger) { log.Info("test", 10) }, func(fields Fields) { assert.Equal(t, "test10", fields["msg"]) }) } func TestInfoShouldNotAddSpacesBetweenStrings(t *testing.T) { LogAndAssertJSON(t, func(log *Logger) { log.Info("test", "test") }, func(fields Fields) { assert.Equal(t, "testtest", fields["msg"]) }) } func TestWithFieldsShouldAllowAssignments(t *testing.T) { var buffer bytes.Buffer var fields Fields logger := New() logger.Out = &buffer logger.Formatter = new(JSONFormatter) localLog := logger.WithFields(Fields{ "key1": "value1", }) localLog.WithField("key2", "value2").Info("test") err := json.Unmarshal(buffer.Bytes(), &fields) assert.Nil(t, err) assert.Equal(t, "value2", fields["key2"]) assert.Equal(t, "value1", fields["key1"]) buffer = bytes.Buffer{} fields = Fields{} localLog.Info("test") err = json.Unmarshal(buffer.Bytes(), &fields) assert.Nil(t, err) _, ok := fields["key2"] assert.Equal(t, false, ok) assert.Equal(t, "value1", fields["key1"]) } func TestUserSuppliedFieldDoesNotOverwriteDefaults(t *testing.T) { LogAndAssertJSON(t, func(log *Logger) { log.WithField("msg", "hello").Info("test") }, func(fields Fields) { assert.Equal(t, "test", fields["msg"]) }) } func TestUserSuppliedMsgFieldHasPrefix(t *testing.T) { LogAndAssertJSON(t, func(log *Logger) { log.WithField("msg", "hello").Info("test") }, func(fields Fields) { assert.Equal(t, "test", fields["msg"]) assert.Equal(t, "hello", fields["fields.msg"]) }) } func TestUserSuppliedTimeFieldHasPrefix(t *testing.T) { LogAndAssertJSON(t, func(log *Logger) { log.WithField("time", "hello").Info("test") }, func(fields Fields) { assert.Equal(t, "hello", fields["fields.time"]) }) } func TestUserSuppliedLevelFieldHasPrefix(t *testing.T) { LogAndAssertJSON(t, func(log *Logger) { log.WithField("level", 1).Info("test") }, func(fields Fields) { assert.Equal(t, "info", fields["level"]) assert.Equal(t, 1.0, fields["fields.level"]) // JSON has floats only }) } func TestDefaultFieldsAreNotPrefixed(t *testing.T) { LogAndAssertText(t, func(log *Logger) { ll := log.WithField("herp", "derp") ll.Info("hello") ll.Info("bye") }, func(fields map[string]string) { for _, fieldName := range []string{"fields.level", "fields.time", "fields.msg"} { if _, ok := fields[fieldName]; ok { t.Fatalf("should not have prefixed %q: %v", fieldName, fields) } } }) } func TestWithTimeShouldOverrideTime(t *testing.T) { now := time.Now().Add(24 * time.Hour) LogAndAssertJSON(t, func(log *Logger) { log.WithTime(now).Info("foobar") }, func(fields Fields) { assert.Equal(t, fields["time"], now.Format(time.RFC3339)) }) } func TestWithTimeShouldNotOverrideFields(t *testing.T) { now := time.Now().Add(24 * time.Hour) LogAndAssertJSON(t, func(log *Logger) { log.WithField("herp", "derp").WithTime(now).Info("blah") }, func(fields Fields) { assert.Equal(t, fields["time"], now.Format(time.RFC3339)) assert.Equal(t, fields["herp"], "derp") }) } func TestWithFieldShouldNotOverrideTime(t *testing.T) { now := time.Now().Add(24 * time.Hour) LogAndAssertJSON(t, func(log *Logger) { log.WithTime(now).WithField("herp", "derp").Info("blah") }, func(fields Fields) { assert.Equal(t, fields["time"], now.Format(time.RFC3339)) assert.Equal(t, fields["herp"], "derp") }) } func TestTimeOverrideMultipleLogs(t *testing.T) { var buffer bytes.Buffer var firstFields, secondFields Fields logger := New() logger.Out = &buffer formatter := new(JSONFormatter) formatter.TimestampFormat = time.StampMilli logger.Formatter = formatter llog := logger.WithField("herp", "derp") llog.Info("foo") err := json.Unmarshal(buffer.Bytes(), &firstFields) assert.NoError(t, err, "should have decoded first message") buffer.Reset() time.Sleep(10 * time.Millisecond) llog.Info("bar") err = json.Unmarshal(buffer.Bytes(), &secondFields) assert.NoError(t, err, "should have decoded second message") assert.NotEqual(t, firstFields["time"], secondFields["time"], "timestamps should not be equal") } func TestDoubleLoggingDoesntPrefixPreviousFields(t *testing.T) { var buffer bytes.Buffer var fields Fields logger := New() logger.Out = &buffer logger.Formatter = new(JSONFormatter) llog := logger.WithField("context", "eating raw fish") llog.Info("looks delicious") err := json.Unmarshal(buffer.Bytes(), &fields) assert.NoError(t, err, "should have decoded first message") assert.Equal(t, len(fields), 4, "should only have msg/time/level/context fields") assert.Equal(t, fields["msg"], "looks delicious") assert.Equal(t, fields["context"], "eating raw fish") buffer.Reset() llog.Warn("omg it is!") err = json.Unmarshal(buffer.Bytes(), &fields) assert.NoError(t, err, "should have decoded second message") assert.Equal(t, len(fields), 4, "should only have msg/time/level/context fields") assert.Equal(t, "omg it is!", fields["msg"]) assert.Equal(t, "eating raw fish", fields["context"]) assert.Nil(t, fields["fields.msg"], "should not have prefixed previous `msg` entry") } func TestNestedLoggingReportsCorrectCaller(t *testing.T) { var buffer bytes.Buffer var fields Fields logger := New() logger.Out = &buffer logger.Formatter = new(JSONFormatter) logger.ReportCaller = true llog := logger.WithField("context", "eating raw fish") llog.Info("looks delicious") _, _, line, _ := runtime.Caller(0) err := json.Unmarshal(buffer.Bytes(), &fields) require.NoError(t, err, "should have decoded first message") assert.Equal(t, 6, len(fields), "should have msg/time/level/func/context fields") assert.Equal(t, "looks delicious", fields["msg"]) assert.Equal(t, "eating raw fish", fields["context"]) assert.Equal(t, "github.com/sirupsen/logrus_test.TestNestedLoggingReportsCorrectCaller", fields["func"]) cwd, err := os.Getwd() require.NoError(t, err) assert.Equal(t, filepath.ToSlash(fmt.Sprintf("%s/logrus_test.go:%d", cwd, line-1)), filepath.ToSlash(fields["file"].(string))) buffer.Reset() logger.WithFields(Fields{ "Clyde": "Stubblefield", }).WithFields(Fields{ "Jab'o": "Starks", }).WithFields(Fields{ "uri": "https://www.youtube.com/watch?v=V5DTznu-9v0", }).WithFields(Fields{ "func": "y drummer", }).WithFields(Fields{ "James": "Brown", }).Print("The hardest workin' man in show business") _, _, line, _ = runtime.Caller(0) err = json.Unmarshal(buffer.Bytes(), &fields) assert.NoError(t, err, "should have decoded second message") assert.Equal(t, 11, len(fields), "should have all builtin fields plus foo,bar,baz,...") assert.Equal(t, "Stubblefield", fields["Clyde"]) assert.Equal(t, "Starks", fields["Jab'o"]) assert.Equal(t, "https://www.youtube.com/watch?v=V5DTznu-9v0", fields["uri"]) assert.Equal(t, "y drummer", fields["fields.func"]) assert.Equal(t, "Brown", fields["James"]) assert.Equal(t, "The hardest workin' man in show business", fields["msg"]) assert.Nil(t, fields["fields.msg"], "should not have prefixed previous `msg` entry") assert.Equal(t, "github.com/sirupsen/logrus_test.TestNestedLoggingReportsCorrectCaller", fields["func"]) require.NoError(t, err) assert.Equal(t, filepath.ToSlash(fmt.Sprintf("%s/logrus_test.go:%d", cwd, line-1)), filepath.ToSlash(fields["file"].(string))) logger.ReportCaller = false // return to default value } func logLoop(iterations int, reportCaller bool) { var buffer bytes.Buffer logger := New() logger.Out = &buffer logger.Formatter = new(JSONFormatter) logger.ReportCaller = reportCaller for i := 0; i < iterations; i++ { logger.Infof("round %d of %d", i, iterations) } } // Assertions for upper bounds to reporting overhead func TestCallerReportingOverhead(t *testing.T) { iterations := 5000 before := time.Now() logLoop(iterations, false) during := time.Now() logLoop(iterations, true) after := time.Now() elapsedNotReporting := during.Sub(before).Nanoseconds() elapsedReporting := after.Sub(during).Nanoseconds() maxDelta := 1 * time.Second assert.WithinDuration(t, during, before, maxDelta, "%d log calls without caller name lookup takes less than %d second(s) (was %d nanoseconds)", iterations, maxDelta.Seconds(), elapsedNotReporting) assert.WithinDuration(t, after, during, maxDelta, "%d log calls without caller name lookup takes less than %d second(s) (was %d nanoseconds)", iterations, maxDelta.Seconds(), elapsedReporting) } // benchmarks for both with and without caller-function reporting func BenchmarkWithoutCallerTracing(b *testing.B) { for i := 0; i < b.N; i++ { logLoop(1000, false) } } func BenchmarkWithCallerTracing(b *testing.B) { for i := 0; i < b.N; i++ { logLoop(1000, true) } } func TestConvertLevelToString(t *testing.T) { assert.Equal(t, "trace", TraceLevel.String()) assert.Equal(t, "debug", DebugLevel.String()) assert.Equal(t, "info", InfoLevel.String()) assert.Equal(t, "warning", WarnLevel.String()) assert.Equal(t, "error", ErrorLevel.String()) assert.Equal(t, "fatal", FatalLevel.String()) assert.Equal(t, "panic", PanicLevel.String()) } func TestParseLevel(t *testing.T) { l, err := ParseLevel("panic") assert.Nil(t, err) assert.Equal(t, PanicLevel, l) l, err = ParseLevel("PANIC") assert.Nil(t, err) assert.Equal(t, PanicLevel, l) l, err = ParseLevel("fatal") assert.Nil(t, err) assert.Equal(t, FatalLevel, l) l, err = ParseLevel("FATAL") assert.Nil(t, err) assert.Equal(t, FatalLevel, l) l, err = ParseLevel("error") assert.Nil(t, err) assert.Equal(t, ErrorLevel, l) l, err = ParseLevel("ERROR") assert.Nil(t, err) assert.Equal(t, ErrorLevel, l) l, err = ParseLevel("warn") assert.Nil(t, err) assert.Equal(t, WarnLevel, l) l, err = ParseLevel("WARN") assert.Nil(t, err) assert.Equal(t, WarnLevel, l) l, err = ParseLevel("warning") assert.Nil(t, err) assert.Equal(t, WarnLevel, l) l, err = ParseLevel("WARNING") assert.Nil(t, err) assert.Equal(t, WarnLevel, l) l, err = ParseLevel("info") assert.Nil(t, err) assert.Equal(t, InfoLevel, l) l, err = ParseLevel("INFO") assert.Nil(t, err) assert.Equal(t, InfoLevel, l) l, err = ParseLevel("debug") assert.Nil(t, err) assert.Equal(t, DebugLevel, l) l, err = ParseLevel("DEBUG") assert.Nil(t, err) assert.Equal(t, DebugLevel, l) l, err = ParseLevel("trace") assert.Nil(t, err) assert.Equal(t, TraceLevel, l) l, err = ParseLevel("TRACE") assert.Nil(t, err) assert.Equal(t, TraceLevel, l) _, err = ParseLevel("invalid") assert.Equal(t, "not a valid logrus Level: \"invalid\"", err.Error()) } func TestLevelString(t *testing.T) { var loggerlevel Level = 32000 _ = loggerlevel.String() } func TestGetSetLevelRace(t *testing.T) { wg := sync.WaitGroup{} for i := 0; i < 100; i++ { wg.Add(1) go func(i int) { defer wg.Done() if i%2 == 0 { SetLevel(InfoLevel) } else { GetLevel() } }(i) } wg.Wait() } func TestLoggingRace(t *testing.T) { logger := New() var wg sync.WaitGroup wg.Add(100) for i := 0; i < 100; i++ { go func() { logger.Info("info") wg.Done() }() } wg.Wait() } func TestLoggingRaceWithHooksOnEntry(t *testing.T) { logger := New() hook := new(ModifyHook) logger.AddHook(hook) entry := logger.WithField("context", "clue") var ( wg sync.WaitGroup mtx sync.Mutex start bool ) cond := sync.NewCond(&mtx) wg.Add(100) for i := 0; i < 50; i++ { go func() { cond.L.Lock() for !start { cond.Wait() } cond.L.Unlock() for j := 0; j < 100; j++ { entry.Info("info") } wg.Done() }() } for i := 0; i < 50; i++ { go func() { cond.L.Lock() for !start { cond.Wait() } cond.L.Unlock() for j := 0; j < 100; j++ { entry.WithField("another field", "with some data").Info("info") } wg.Done() }() } cond.L.Lock() start = true cond.L.Unlock() cond.Broadcast() wg.Wait() } func TestReplaceHooks(t *testing.T) { old, cur := &TestHook{}, &TestHook{} logger := New() logger.SetOutput(ioutil.Discard) logger.AddHook(old) hooks := make(LevelHooks) hooks.Add(cur) replaced := logger.ReplaceHooks(hooks) logger.Info("test") assert.Equal(t, old.Fired, false) assert.Equal(t, cur.Fired, true) logger.ReplaceHooks(replaced) logger.Info("test") assert.Equal(t, old.Fired, true) } // Compile test func TestLogrusInterfaces(t *testing.T) { var buffer bytes.Buffer // This verifies FieldLogger and Ext1FieldLogger work as designed. // Please don't use them. Use Logger and Entry directly. fn := func(xl Ext1FieldLogger) { var l FieldLogger = xl b := l.WithField("key", "value") b.Debug("Test") } // test logger logger := New() logger.Out = &buffer fn(logger) // test Entry e := logger.WithField("another", "value") fn(e) } // Implements io.Writer using channels for synchronization, so we can wait on // the Entry.Writer goroutine to write in a non-racey way. This does assume that // there is a single call to Logger.Out for each message. type channelWriter chan []byte func (cw channelWriter) Write(p []byte) (int, error) { cw <- p return len(p), nil } func TestEntryWriter(t *testing.T) { cw := channelWriter(make(chan []byte, 1)) log := New() log.Out = cw log.Formatter = new(JSONFormatter) _, err := log.WithField("foo", "bar").WriterLevel(WarnLevel).Write([]byte("hello\n")) if err != nil { t.Error("unexecpted error", err) } bs := <-cw var fields Fields err = json.Unmarshal(bs, &fields) assert.Nil(t, err) assert.Equal(t, fields["foo"], "bar") assert.Equal(t, fields["level"], "warning") } func TestLogLevelEnabled(t *testing.T) { log := New() log.SetLevel(PanicLevel) assert.Equal(t, true, log.IsLevelEnabled(PanicLevel)) assert.Equal(t, false, log.IsLevelEnabled(FatalLevel)) assert.Equal(t, false, log.IsLevelEnabled(ErrorLevel)) assert.Equal(t, false, log.IsLevelEnabled(WarnLevel)) assert.Equal(t, false, log.IsLevelEnabled(InfoLevel)) assert.Equal(t, false, log.IsLevelEnabled(DebugLevel)) assert.Equal(t, false, log.IsLevelEnabled(TraceLevel)) log.SetLevel(FatalLevel) assert.Equal(t, true, log.IsLevelEnabled(PanicLevel)) assert.Equal(t, true, log.IsLevelEnabled(FatalLevel)) assert.Equal(t, false, log.IsLevelEnabled(ErrorLevel)) assert.Equal(t, false, log.IsLevelEnabled(WarnLevel)) assert.Equal(t, false, log.IsLevelEnabled(InfoLevel)) assert.Equal(t, false, log.IsLevelEnabled(DebugLevel)) assert.Equal(t, false, log.IsLevelEnabled(TraceLevel)) log.SetLevel(ErrorLevel) assert.Equal(t, true, log.IsLevelEnabled(PanicLevel)) assert.Equal(t, true, log.IsLevelEnabled(FatalLevel)) assert.Equal(t, true, log.IsLevelEnabled(ErrorLevel)) assert.Equal(t, false, log.IsLevelEnabled(WarnLevel)) assert.Equal(t, false, log.IsLevelEnabled(InfoLevel)) assert.Equal(t, false, log.IsLevelEnabled(DebugLevel)) assert.Equal(t, false, log.IsLevelEnabled(TraceLevel)) log.SetLevel(WarnLevel) assert.Equal(t, true, log.IsLevelEnabled(PanicLevel)) assert.Equal(t, true, log.IsLevelEnabled(FatalLevel)) assert.Equal(t, true, log.IsLevelEnabled(ErrorLevel)) assert.Equal(t, true, log.IsLevelEnabled(WarnLevel)) assert.Equal(t, false, log.IsLevelEnabled(InfoLevel)) assert.Equal(t, false, log.IsLevelEnabled(DebugLevel)) assert.Equal(t, false, log.IsLevelEnabled(TraceLevel)) log.SetLevel(InfoLevel) assert.Equal(t, true, log.IsLevelEnabled(PanicLevel)) assert.Equal(t, true, log.IsLevelEnabled(FatalLevel)) assert.Equal(t, true, log.IsLevelEnabled(ErrorLevel)) assert.Equal(t, true, log.IsLevelEnabled(WarnLevel)) assert.Equal(t, true, log.IsLevelEnabled(InfoLevel)) assert.Equal(t, false, log.IsLevelEnabled(DebugLevel)) assert.Equal(t, false, log.IsLevelEnabled(TraceLevel)) log.SetLevel(DebugLevel) assert.Equal(t, true, log.IsLevelEnabled(PanicLevel)) assert.Equal(t, true, log.IsLevelEnabled(FatalLevel)) assert.Equal(t, true, log.IsLevelEnabled(ErrorLevel)) assert.Equal(t, true, log.IsLevelEnabled(WarnLevel)) assert.Equal(t, true, log.IsLevelEnabled(InfoLevel)) assert.Equal(t, true, log.IsLevelEnabled(DebugLevel)) assert.Equal(t, false, log.IsLevelEnabled(TraceLevel)) log.SetLevel(TraceLevel) assert.Equal(t, true, log.IsLevelEnabled(PanicLevel)) assert.Equal(t, true, log.IsLevelEnabled(FatalLevel)) assert.Equal(t, true, log.IsLevelEnabled(ErrorLevel)) assert.Equal(t, true, log.IsLevelEnabled(WarnLevel)) assert.Equal(t, true, log.IsLevelEnabled(InfoLevel)) assert.Equal(t, true, log.IsLevelEnabled(DebugLevel)) assert.Equal(t, true, log.IsLevelEnabled(TraceLevel)) } func TestReportCallerOnTextFormatter(t *testing.T) { l := New() l.Formatter.(*TextFormatter).ForceColors = true l.Formatter.(*TextFormatter).DisableColors = false l.WithFields(Fields{"func": "func", "file": "file"}).Info("test") l.Formatter.(*TextFormatter).ForceColors = false l.Formatter.(*TextFormatter).DisableColors = true l.WithFields(Fields{"func": "func", "file": "file"}).Info("test") } 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() }