code: func ReadInt64(file string) (int64, error) {
  	f, err := os.Open(file)
  	if err != nil {
  		return 0, err
  	}
  	defer f.Close()
  
  	buf := make([]byte, 19)
  	n, err := f.Read(buf)
  	if err != nil {
  		return 0, err
  	}
  
  	p := strings.Split(string(buf[0:n]), "\n")
  	v, err := strconv.ParseInt(p[0], 10, 64)
  	if err != nil {
  		return 0, err
  	}
  
  	return v, nil
  }
docs: // ReadInt64 reads one int64 number from the first line of a file.