diff --git a/console_formatter.go b/console_formatter.go
index f4eee07..5a5bb6d 100644
--- a/console_formatter.go
+++ b/console_formatter.go
@@ -1,3 +1,17 @@
+// Copyright 2020 The ZKits Project Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package logger
 
 import (
diff --git a/console_formatter_caller_test.go b/console_formatter_caller_test.go
index d6dfb68..75fc599 100644
--- a/console_formatter_caller_test.go
+++ b/console_formatter_caller_test.go
@@ -1,3 +1,17 @@
+// Copyright 2020 The ZKits Project Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package logger
 
 import (
@@ -14,9 +28,9 @@ func TestConsoleFormatter_Format_WithoutCaller(t *testing.T) {
 	buf := new(bytes.Buffer)
 	l.SetOutput(buf)
 
-	l.WithField("foo", 1).WithCaller().Trace("test") // LINE 17
+	l.WithField("foo", 1).WithCaller().Trace("test") // LINE 31
 	fmt.Println(buf.String())
-	want := "[TIME][\u001B[36mTAC\u001B[0m] test console_formatter_caller_test.go:17 foo=1\n"
+	want := "[TIME][\u001B[36mTAC\u001B[0m] test console_formatter_caller_test.go:31 foo=1\n"
 	if want != buf.String() {
 		t.Fatalf("NewConsoleFormatter().Format(): %s", strconv.Quote(buf.String()))
 	}
diff --git a/console_formatter_test.go b/console_formatter_test.go
index cf919fd..5a09af6 100644
--- a/console_formatter_test.go
+++ b/console_formatter_test.go
@@ -1,3 +1,17 @@
+// Copyright 2020 The ZKits Project Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package logger
 
 import (
diff --git a/multi_writer.go b/multi_writer.go
index cd02679..94ea0fe 100644
--- a/multi_writer.go
+++ b/multi_writer.go
@@ -1,3 +1,17 @@
+// Copyright 2020 The ZKits Project Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package logger
 
 import (
diff --git a/multi_writer_test.go b/multi_writer_test.go
index d70a980..211c4e8 100644
--- a/multi_writer_test.go
+++ b/multi_writer_test.go
@@ -1,3 +1,17 @@
+// Copyright 2020 The ZKits Project Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package logger
 
 import (