Async await sample which explains the flow of execution.

async.dart

import 'dart:async';

Future<void> printOrderMessage() async {
  print('printOrderMessage: Awaiting user order... fetches and returns Future<void>');
  var order = await fetchUserOrder();
  print('This and following execute only after Future is complete');
  print('Your order is: $order');
}

Future<String> fetchUserOrder() {
  print('fetchUserOrder: going to order with delay');
  return Future.delayed(const Duration(seconds: 3), () => 'Large Latte');
}

void main() {
  countSeconds(4);
  print(printOrderMessage());
  print('exiting main()');
}

void countSeconds(int s) {
  for (var i = 1; i <= s; i++) {
    // Registering into EventQueue of main isolate.
    Future.delayed(Duration(seconds: i), () => print(i));
  }
}