/**
* save session and responder as $request's attribute.
*
* @param ServerRequestInterface $request
* @param ResponseInterface $response
* @param callable $next
* @return mixed
*/
public function __invoke(ServerRequestInterface $request, ResponseInterface $response, callable $next)
{
$request = Respond::withResponder($request, $this->responder);
return $next($request, $response);
}
