code: func nonKeyFile(fi os.FileInfo) bool {
  	// Skip editor backups and UNIX-style hidden files.
  	if strings.HasSuffix(fi.Name(), "~") || strings.HasPrefix(fi.Name(), ".") {
  		return true
  	}
  	// Skip misc special files, directories (yes, symlinks too).
  	if fi.IsDir() || fi.Mode()&os.ModeType != 0 {
  		return true
  	}
  	return false
  }
docs: // nonKeyFile ignores editor backups, hidden files and folders/symlinks.