invoke method
Implementation
@override
String invoke(String method, params, callback) {
  if (method == 'goTo') {
    assert(params is String, 'URL must be string.');
    goTo(params);
  }
  return '';
}@override
String invoke(String method, params, callback) {
  if (method == 'goTo') {
    assert(params is String, 'URL must be string.');
    goTo(params);
  }
  return '';
}