code: func ReadDir(dirpath string) ([]string, error) {
  	dir, err := os.Open(dirpath)
  	if err != nil {
  		return nil, err
  	}
  	defer dir.Close()
  	names, err := dir.Readdirnames(-1)
  	if err != nil {
  		return nil, err
  	}
  	sort.Strings(names)
  	return names, nil
  }
docs: // ReadDir returns the filenames in the given directory in sorted order.