close method
Shuts down the isolate.
Implementation
Future<void> close() async {
if (_isClosed) return;
_isClosed = true;
final (toChild, fromChild, inflight) = await _connected;
// Fail any outstanding requests.
for (final c in inflight.values) {
if (!c.isCompleted) {
c.completeError(StateError('$runtimeType is closed'));
}
}
inflight.clear();
toChild.send(null);
fromChild.close();
}