register method
Registers a callback that will be called when the CancellationToken is canceled.
Implementation
CancellationTokenRegistration register(CallbackRegistration? callback,
[Object? state]) {
var source = _source;
if (callback == null) {
throw ArgumentError.notNull('callback');
}
if (source != null) {
return source.register(callback, state);
}
return CancellationTokenRegistration(0, null);
}