Синхронное выполнение кода SWIFT alamofire?

spoiler

func download_all_audio(lesson: LessonClass)
    {
        Mainlesson = [lesson]
        
        for (tl, l) in Mainlesson[0].cards.enumerated() {
            start_download(url: l.Audio, t:tl) {
                
            }
        }
        
        print("============")
        print(self.Mainlesson[0].cards[0].LocalAudio)
    }

func start_download(url: String, t: Int, completion: @escaping () -> Void)
    {
        guard let url = URL.init(string: url) else {
            print("error url")
            return
        }
        
        let destination = DownloadRequest.suggestedDownloadDestination(for: .documentDirectory)
        
        Alamofire.download(url, to: destination)
            .downloadProgress { progress in
                //print("Download Progress: \(String(progress.fractionCompleted))")
            }
            .responseData { response in
                self.Mainlesson[0].cards[t].LocalAudio = response.destinationURL!.absoluteString
        }
        
        completion()
    }