code: func Int64() int64 {
  	var bs [8]byte
  	_, err := io.ReadFull(cryptoRand.Reader, bs[:])
  	if err != nil {
  		panic("randomness failure: " + err.Error())
  	}
  	return int64(binary.BigEndian.Uint64(bs[:]))
  }
docs: // Int64 returns a strongly random int64