code: func bytes2int(data []byte) uint64 {
  	n, val := len(data), uint64(0)
  	if n > 8 {
  		panic("data too long")
  	}
  
  	for i, b := range data {
  		val += uint64(b) << uint64((n-i-1)*8)
  	}
  	return val
  }
docs: // bytes2int returns the int value it represents.