code: func IsControllerMounted(c string) (bool, error) {
  	cgroupProcsPath := filepath.Join("/sys/fs/cgroup", c, "cgroup.procs")
  	if _, err := os.Stat(cgroupProcsPath); err != nil {
  		if !os.IsNotExist(err) {
  			return false, err
  		}
  		return false, nil
  	}
  
  	return true, nil
  }
docs: // IsControllerMounted returns whether a controller is mounted by checking that
  // cgroup.procs is accessible