APIExtension.swift

extension iTunesAPIClient: URLSessionDelegate {
    internal func urlSessionDidFinishEvents(forBackgroundURLSession session: URLSession) {
         // Calls background session completion in AppDelegate
    }
    
    internal func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64,totalBytesExpectedToWrite: Int64) {
        // Gives you the URLSessionDownloadTask that is being executed
        // along with the total file length - totalBytesExpectedToWrite
        // and the current amount of data that has received up to this point - totalBytesWritten
   }
}