code: func Load64(hexkey string) (*[64]byte, error) {
  	if len(hexkey) != 128 {
  		return nil, fmt.Errorf("nacl: incorrect hex key length: %d, should be 64", len(hexkey))
  	}
  	keyBytes, err := hex.DecodeString(hexkey)
  	if err != nil {
  		return nil, err
  	}
  	if len(keyBytes) != 64 {
  		return nil, fmt.Errorf("nacl: incorrect key length: %d", len(keyBytes))
  	}
  	key := new([64]byte)
  	copy(key[:], keyBytes)
  	return key, nil
  }
docs: // Load decodes a 128-byte hex string into a Key. A hex key is suitable for
  // representation in a configuration file. You can generate one by running
  // nacl/sign.GenerateKey(nil).