请求超时后如何执行函数？

Question

目前我有一个从服务器检索数据的函数。有超时请求五秒钟。我不完全确定超时请求是否正常，因为五秒钟后没有任何反应。当超时请求完成时，我试图让它向用户显示警报视图。这是代码：

 lazy var configuration: URLSessionConfiguration =   URLSessionConfiguration.default

 lazy var session: URLSession = URLSession(configuration: self.configuration)

 typealias JSONData = ((Data) -> Void)

  func getJSONData(type: String, urlExtension: String, completion: @escaping JSONData) {

    configuration.timeoutIntervalForRequest = 5
    configuration.timeoutIntervalForResource = 5

    let request = URLRequest(url: URL(string:"\(baseURL)\(type)/\(urlExtension)?api_key=\(apiKey)&region=US&append_to_response=videos,images,releases")! )

    let dataTask = session.dataTask(with: request, completionHandler: { (data, response, error) in

      if error == nil {
        if let httpResponse = response as? HTTPURLResponse {
          switch (httpResponse.statusCode) {
          case 200:
            if let data = data {
              completion(data)
            }
          default:
            print(httpResponse.statusCode)
          }
        }
      } else {
        print("Error: \(error?.localizedDescription)")
      }
    })
    dataTask.resume()
  }