Fix: go vet requires at least a go file in the root package folder

Changelog: none

Signed-off-by: Fabio Tranchitella <[email protected]>

main_test.go

@@ -0,0 +1,15 @@
+// Copyright 2020 Northern.tech AS
+//
+//    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 main