AsyncRx.Net Switch subscribes to newer and then unsubscribes from older and not vice versa

[fedeAlterio]

Consider this code

var timer1 = AsyncObservable.Interval(TimeSpan.FromSeconds(1))
                            .Do(x => Console.WriteLine($"Timer 1 tick {x}"), e => { }, () => { })
                            .Finally(() => Console.WriteLine("Unsubscribed from timer 1"));

var timer2 = AsyncObservable.DeferAsync(async () =>
{
    Console.WriteLine("Subscribing timer 2");
    await Task.Delay(100);
    return AsyncObservable.Interval(TimeSpan.FromMilliseconds(100))
                          .Finally(async () =>
                          {
                              Console.WriteLine("Unsubscribing timer 2");
                              await Task.Delay(1000);
                              Console.WriteLine("Unsubscribed timer 2");
                          });
});

await timer1.Select(_ => timer2)
            .Take(3)
            .Switch()
            .SubscribeAsync(_ => {});

Console.Read();

The output is

Timer 1 tick 0
Subscribing timer 2
Timer 1 tick 1
Subscribing timer 2
Unsubscribing timer 2
Unsubscribed timer 2
Timer 1 tick 2
Subscribing timer 2
Unsubscribing timer 2
Unsubscribed timer 2
Unsubscribed from timer 1

This is incorrect, since it first subscribes to the newer observable, and then it unsubscribes from the previous.
The issue that it first subscribes to the inner observable, and the assign it to the serialDisposable, that disposes the older, but its too late since we are already subscribed!

reactive/AsyncRx.NET/System.Reactive.Async/Linq/Operators/Switch.cs

Lines 96 to 98 in 1ce85f4

	var inner = await xs.SubscribeSafeAsync(innerObserver).ConfigureAwait(false);
	await disposable.AssignAsync(inner).ConfigureAwait(false);

If you want I can provide a PR with the fix