Spawning new isolates in Dart is easy if you know how to do it:

main.dart

import 'dart:isolate';
import 'dart:async';

void main() {
  Future isolate1 = Isolate.spawnUri(Uri.parse('isolate.dart'), [], null);
  Future isolate2 = Isolate.spawnUri(Uri.parse('isolate.dart'), [], null);
  Future.wait([isolate1,isolate2]);
  while(true);
}

Future.wait only waits until the two isolates are spawned. If the main application stops running, the two spawned isolates will stop running as well. That’s why we need a while(true)-loop here.

The isolate itself looks like this:

library isolate;

void main() {
  print('isolate.main()');
  while(true);
}

The two arguments after the URI are used for a list of arguments and an optional message. If you want to use this, just modify the main method of your isolate:

void main(args) {...}
void main(args, message) {...}