WorkerMessageHandler typedef
WorkerMessageHandler =
void Function(Object? payload)
Signature of the handler invoked when the page sends a free-form message
to the background worker (see WorkmanagerWeb.sendMessageToWorker).
The handler runs in the same context as the task handler (Web Worker, Service Worker or in-page fallback), so it must stay Flutter-free too.
Implementation
typedef WorkerMessageHandler = void Function(Object? payload);