code: func DecompressPubkey(pubkey []byte) (*ecdsa.PublicKey, error) {
  	if len(pubkey) != 33 {
  		return nil, errors.New("invalid compressed public key length")
  	}
  	key, err := btcec.ParsePubKey(pubkey, btcec.S256())
  	if err != nil {
  		return nil, err
  	}
  	return key.ToECDSA(), nil
  }
docs: // DecompressPubkey parses a public key in the 33-byte compressed format.