我的JSON提取方法只获取一次

Question

我有从JSON文件中获取数据的方法。它工作正常，当我第一次运行应用程序时，但当我更新JSON文件中的数据并回顾我的应用程序时，数据不会更改。我必须删除应用并再次上传。我的代码出了什么问题？

let requestURL: NSURL = NSURL(string: "https://www.example.com/json.txt")!
        let urlRequest: NSMutableURLRequest = NSMutableURLRequest(url: requestURL as URL)
        let session = URLSession.shared
        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) {
                print("Everything is fine, file downloaded successfully.")

                do{

                    let json = try JSONSerialization.jsonObject(with: data!, options:.allowFragments) as! [String: AnyObject]
                    if let JSONSchools = json["skoly"] as? [[String: AnyObject]]{

                        for school in JSONSchools {

                            if let name = school["nazev"] as? String {

                                if let city = school["mesto"] as? String {

                                    if let id = school["id"] as? String {
                                        self.schools.append(School.init(name: name, city: city, id: id))
                                    }

                                }

                            }
                        }
                        self.fetchFinished = true
                    }

                } catch {
                    print("Error with Json: \(error)")
                }
            }
        }

        task.resume()
    }

感谢您的帮助