在iPhone 7网络4g上没有响应的URLSessionDataTask

Question

仅在网络类型为4g的iPhone 7上遇到 URLSessionDataTask 问题，网络类型为WiFi的设备运行相同。任何人都可以帮助我吗？

这是Swift 3中的代码：

func getParentAccount(onGetParentAccountComplete: OnGetParentAccountComplete) {

    let url = URL(string: "http://...")!
    let authorizationHeader = authorizationHeaderFactory.getOAuth2Authorization()

    var request = URLRequest(url: url)
    request.setValue(authorizationHeader["Authorization"], forHTTPHeaderField: "Authorization")
    request.addValue("application/json", forHTTPHeaderField: "Accept")
    request.httpMethod = "GET"

    let task = URLSession.shared.dataTask(with: request) { data, response, error in
        guard let data = data, error == nil else {                                                 // check for fundamental networking error
            // error
            print("Error: \(String(describing: error))")
            onGetParentAccountComplete.onGetParentAccountFailure(message: "Communication error")
            return
        }

        if let httpStatus = response as? HTTPURLResponse, httpStatus.statusCode == 200, let json = try? JSONSerialization.jsonObject(with: data, options: []) {
            // ok
            let parentAccountDTO = self.parentAccountMapper.mapJSONToDTO(json: json as! [String : Any])
            onGetParentAccountComplete.onGetParentAccountSuccess(parentAccount: self.parentAccountMapper.mapDomain(source: parentAccountDTO))

            return
        } else {
            // error
            print("Error: response = \(String(describing: response))")
            onGetParentAccountComplete.onGetParentAccountFailure(message: "Error response")
            return
        }
    }

    task.resume()
}