Swift: Downloading and saving a custom file from the Internet

Question

I would like my application to download a file with custom extension from the Internet and save it. I have written the following code:

import UIKit
class ViewController: UIViewController {

let url_to_my_file: URL = (URL(string: "https://my-url.com/file1.tcr"))!

override func viewDidLoad() {
    super.viewDidLoad()

    Downloader.load(url: url_to_my_file) {
        print("done")
    }
  }
}

====

import Foundation

class Downloader {

static let instanse = Downloader()

class func load(url: URL, completion: @escaping () -> ()) {

    let documentsURL = NSURL(fileURLWithPath: NSSearchPathForDirectoriesInDomains( .documentDirectory, .userDomainMask, true).first!, isDirectory: true)
    let localUrl = documentsURL.appendingPathComponent("file.tcr")!

    let sessionConfig = URLSessionConfiguration.default
    let session = URLSession(configuration: sessionConfig)
    var request = try! URLRequest(url: url)
    request.httpMethod = "GET"

    let task = session.downloadTask(with: request) { (tempLocalUrl, response, error) in
        if let tempLocalUrl = tempLocalUrl, error == nil {
            // Success
            if let statusCode = (response as? HTTPURLResponse)?.statusCode {
                print("Success: \(statusCode)")
            }

            do {
                try FileManager.default.copyItem(at: tempLocalUrl, to: localUrl)
                completion()
            } catch (let writeError) {
                print("error writing file \(localUrl) : \(writeError)")
            }

        } else {
            print("Failure: %@", error?.localizedDescription);
        }
    }
    task.resume()
  }
}

However, when i run it, i get messages in console that my code does not conform to ATS policy.

2018-07-12 21:44:31.965978+0300 dl_test[5294:4397157] App Transport Security
has blocked a cleartext HTTP (http://) resource load since it is insecure.
Temporary exceptions can be configured via your app's Info.plist file.
2018-07-12 21:44:31.966028+0300 dl_test[5294:4397157] Cannot start load of Task
<52F90327-B8A3-436D-B68C-716EBACFF0BF>.<1> since it does not conform to ATS
policy
2018-07-12 21:44:31.966121+0300 dl_test[5294:4397159] Task <52F90327-B8A3-436D-
B68C-716EBACFF0BF>.<1> finished with error - code: -1022
Failure: %@ Optional("The resource could not be loaded because the App
Transport Security policy requires the use of a secure connection.")

Weird thing, if i put let url_to_my_file: URL = (URL(string: "https://my-url.com/file2.txt"))! instead of let url_to_my_file: URL = (URL(string: "https://my-url.com/file1.tcr"))!, everything works without mistakes, file is saved and dowloaded. I tried swapping extension of the file1 into .txt, but it didn't change anything.

I believed that all i needed to do to conform to that ATS policy is make sure that I use HTTPS, and not HTTP links. Are there any other specific requirements for certain data types, or am i making some other mistake in my code?

I would like to conform to the policy, without using workarounds like editing info.plist. Is there a way to do it?

p.s. usage of Alamofire or any other pods for my project is not allowed, unfortunately

p.p.s i am aware about this topic Transport security has blocked a cleartext HTTP, however the responders offer workaround via editing inof.plist and that's not the solution that i'm looking for