code: func (ftp *FTP) Size(path string) (size int, err error) {
  	line, err := ftp.cmd("213", "SIZE %s", path)
  
  	if err != nil {
  		return 0, err
  	}
  
  	return strconv.Atoi(line[4 : len(line)-2])
  }
docs: // Size returns the size of a file.