gistfile1.txt

private var continuation: 
AsyncThrowingStream<Double, Error>.Continuation?

func urlSession(_ session: URLSession,
                downloadTask: URLSessionDownloadTask,
                didWriteData bytesWritten: Int64,
                totalBytesWritten: Int64,
                totalBytesExpectedToWrite: Int64) {
    guard let continuation else { return }
    
    if totalBytesExpectedToWrite > 0 {
        let progress = Double(totalBytesWritten) / Double(totalBytesExpectedToWrite) * 100
        continuation.yield(progress)
    }
}

func urlSession(_ session: URLSession,
                downloadTask: URLSessionDownloadTask,
                didFinishDownloadingTo location: URL) {
    continuation?.finish()
}

func urlSession(_ session: URLSession,
                task: URLSessionTask,
                didCompleteWithError error: Error?) {
    if let error {
        continuation?.yield(with: .failure(error))
    }
    continuation?.finish()
}