Dart Future example

main.dart

import 'dart:async';
import 'dart:math';

void main() {
  print("The main UI thread starts here.");
  print("Now it will take 10 seconds to display news headlines.");
  displayNews();
  print("The main UI thread ends.");
}

void displayNews() {
  Future<String> displayHeadlines = checkNews();

  displayHeadlines.then((headline) {
    print("Headlines: $headline");
  }).catchError((error) {
    print("An error ocurred: $error");
  }).whenComplete(() {
    print('complete');
  });
}

Future<String> checkNews() {
  return Future.delayed(Duration(seconds: 10), () {
    if (Random().nextBool()) {
      return "UFO LANDED, ALIEN GREETED, WORLD SAVED";
    } else {
      throw Error();
    }
  }).timeout(
    Duration(seconds: 20),
    onTimeout: () => "A timeout occurred",
  );
}