func toKey(tkn jwt.Token) (auth.Key, error) {
	data, err := json.Marshal(tkn.PrivateClaims())
	if err != nil {
		return auth.Key{}, errors.Wrap(ErrJSONHandle, err)
	}
	var key auth.Key
	if err := json.Unmarshal(data, &key); err != nil {
		return auth.Key{}, errors.Wrap(ErrJSONHandle, err)
	}

	tType, ok := tkn.Get(tokenType)
	if !ok {
		return auth.Key{}, err // which the err is nil
	}