Add golint to test (#255)

* Add a new lint rule to the Makefile

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>

* Fix linter errors

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>

* Allow replacing the default apt mirror

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>

supervisor/exit.go

@@ -7,6 +7,7 @@ import (
 	"github.com/docker/containerd/runtime"
 )
 
+// ExitTask holds needed parameters to execute the exit task
 type ExitTask struct {
 	baseTask
 	Process runtime.Process
@@ -56,6 +57,7 @@ func (s *Supervisor) exit(t *ExitTask) error {
 	return nil
 }
 
+// ExecExitTask holds needed parameters to execute the exec exit task
 type ExecExitTask struct {
 	baseTask
 	ID      string