$middleware = new Middleware(function (RequestInterface $request, DelegateInterface $next) {
    // delegate control to next middleware
    return $next($request);
});

$middleware2 = new Middleware(function (RequestInterface $request, DelegateInterface $next) {
    echo 'world';
});

$dispatcher = new Dispatcher([
    $middleware,
    $middleware2
]);

$response = $dispatcher->dispatch(new ServerRequest('GET', '/'));