Improve code coverage unit tests

1 files changed, 1 insertions, 1 deletions

diff --git a/sheet.go b/sheet.go
index 954de5b..2654b8f 100644
--- a/sheet.go
+++ b/sheet.go
@@ -1,4 +1,4 @@
-// Copyright 2016 - 2019 The excelize Authors. All rights reserved. Use of
+// Copyright 2016 - 2020 The excelize Authors. All rights reserved. Use of
 // this source code is governed by a BSD-style license that can be found in
 // the LICENSE file.
 //