code: func unexpected(parser *Parser, atToken lexer.Token) error {
  	var token = atToken
  	if (atToken == lexer.Token{}) {
  		token = parser.Token
  	}
  	description := fmt.Sprintf("Unexpected %v", lexer.GetTokenDesc(token))
  	return gqlerrors.NewSyntaxError(parser.Source, token.Start, description)
  }
docs: // Helper function for creating an error when an unexpected lexed token
  // is encountered.