Реверс Apache, Кэширующий Прокси - почему это не кэширование?

class ViewController: UIViewController {

    let requestURL : NSURL = NSURL(string: "http://www.learnswiftonline.com/Samples/subway.json")!
    let session = URLSession.shared

    override func viewDidLoad() {
        super.viewDidLoad()

        fetchData()
    }

    func fetchData()
    {
        let urlRequest: NSMutableURLRequest = NSMutableURLRequest(url: requestURL as URL)
        let task = session.dataTask(with: urlRequest as URLRequest) { (data, response, error) -> Void in

            let httpResponse = response as! HTTPURLResponse
            let statusCode = httpResponse.statusCode

            if(statusCode == 200)
            {
                do {
                    let jsonResponse = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers)
                    print(jsonResponse as! NSDictionary)
                }
                catch let error
                {
                    print(error)
                }
            }
        }
        task.resume()

    }
}