code: func (ftp *FTP) Syst() (line string, err error) {
  	if err := ftp.send("SYST"); err != nil {
  		return "", err
  	}
  	if line, err = ftp.receive(); err != nil {
  		return
  	}
  	if !strings.HasPrefix(line, StatusSystemType) {
  		err = errors.New(line)
  		return
  	}
  
  	return strings.SplitN(strings.TrimSpace(line), " ", 2)[1], nil
  }
docs: // Syst returns the system type of the remote host