n, err := base64DecodeBytes(token[:i], buf)
	if err != nil {
		return nil, &jwtgo.ValidationError{Inner: err, Errors: jwtgo.ValidationErrorMalformed}
	}
	headerDec := buf[:n]
	buf = buf[n:]

	alg, _, _, err := jsonparser.Get(headerDec, "alg")
	if err != nil {
		return nil, &jwtgo.ValidationError{Inner: err, Errors: jwtgo.ValidationErrorMalformed}
	}

	n, err = base64DecodeBytes(token[i+1:j], buf)