code: func Uint64(v []byte, err error) (uint64, error) {
  	if err != nil {
  		return 0, err
  	} else if v == nil || len(v) == 0 {
  		return 0, nil
  	} else if len(v) != 8 {
  		return 0, errIntNumber
  	}
  
  	return binary.LittleEndian.Uint64(v), nil
  }
docs: // Uint64 gets unsigned 64 integer.