ever<T>  method 
Type-safe convenience worker methods
Implementation
ZenWorkerHandle ever<T>(ValueNotifier<T> obs, void Function(T) callback) {
  return _createWorker(() => ZenWorkers.ever<T>(obs, callback), 'ever');
}Type-safe convenience worker methods
ZenWorkerHandle ever<T>(ValueNotifier<T> obs, void Function(T) callback) {
  return _createWorker(() => ZenWorkers.ever<T>(obs, callback), 'ever');
}