Update worker docs - fix worker sample

[wapmorgan]

We need to avoid infinity cycle

[roxblnfk]

Hello ✋

In your case we have some chance to get undefined $request in the beginning when an external RequestFactory fails on parsing the first request.

I think it will be better to fix it using that code:

// ...

while (true) {
    try {
        $request = $psr7->waitRequest();
        if ($request === null) {
            break;
        }
    } catch (\Throwable $e) {

        // ...

[rustatian]

Thank you guys 👍🏻