onRequest method
Called when the request is about to be sent.
Implementation
@override
Future<void> onRequest(
dio.RequestOptions options, dio.RequestInterceptorHandler handler) async {
super.onRequest(options, handler);
eventList.add(_requests[options] = NetworkEvent.now(
request: options.toRequest(),
error: null,
response: null,
));
return Future.value(options);
}