code: func ChPasswd(user string, key []byte) error {
  	shadow, err := LookupShadow(user)
  	if err != nil {
  		return err
  	}
  	shadow.Passwd(key)
  
  	return edit(user, shadow)
  }
docs: // == Change passwd
  // ChPasswd updates passwd.
  // The passwd must be supplied in clear-text.