code: func (h *DBHeader) GetHmacSha256(hmacKey []byte) (ret [32]byte) {
  	hash := hmac.New(sha256.New, hmacKey)
  	hash.Write(h.RawData)
  	copy(ret[:32], hash.Sum(nil)[:32])
  	return
  }
docs: // GetHmacSha256 returns the HMAC-Sha256 hash of the header