code: func ChGPasswd(group string, key []byte) error {
  	gshadow, err := LookupGShadow(group)
  	if err != nil {
  		return err
  	}
  	gshadow.Passwd(key)
  
  	return edit(group, gshadow)
  }
docs: // ChGPasswd updates group passwd.
  // The passwd must be supplied in clear-text.