iOS URLSession后台下载多任务，手动唤醒App后报错

app在后台使用URLSession多任务下载，手动唤起app后，下载报错

我在背景URLSession中创建了1800个task，然后让App进入后台，过一段时间后（几分钟），手动唤起app进入前台，就会在URLSession的回调中发生了错误。

以下错误在以下delegate中发生：

func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {}

BackgroundSession <B43F4169-5B6D-4928-B90F-6F29BC349A91> error requesting a NSURLSessionDownloadTask from background transfer daemon: Error Domain=NSCocoaErrorDomain Code=4099 "The connection to service named com.apple.nsurlsessiond was interrupted, but the message was sent over an additional proxy and therefore this proxy has become invalid." UserInfo={NSDebugDescription=The connection to service named com.apple.nsurlsessiond was interrupted, but the message was sent over an additional proxy and therefore this proxy has become invalid.}

原因分析

** 因为开启的task太多了，在后台持续了几分钟，可能有些task还未开始。
当我把任务数量改为160时，没有任何问题**