code: func (ftp *FTP) Quit() (err error) {
  	if _, err := ftp.cmd(StatusConnectionClosing, "QUIT"); err != nil {
  		return err
  	}
  
  	ftp.conn.Close()
  	ftp.conn = nil
  
  	return nil
  }
docs: // Quit sends quit to the server and close the connection. No need to Close after this.