code: func NewWALFactory(encrypter encryption.Encrypter, decrypter encryption.Decrypter) WALFactory {
  	return walCryptor{
  		encrypter: encrypter,
  		decrypter: decrypter,
  	}
  }
docs: // NewWALFactory returns an object that can be used to produce objects that
  // will read from and write to encrypted WALs on disk.