Save a video when app is closed or terminated

Question

My app records video and I wanted to stop the video and save it when the app enters background. I found that to run anything during the time the app enters the background you use appdelegate's applicationDidEnterBackground, but it doesn't save the video it only stops the recording.

if(vc.recording){
        print("break")
        vc.recordButton.setBackgroundImage(#imageLiteral(resourceName: "start recording"), for: UIControlState.normal)

        vc.recording = false

        self.vc.videoFileOutput.stopRecording()
        let when = DispatchTime.now() + 0.1 // setting .1 second delay
        DispatchQueue.main.asyncAfter(deadline: when) { //give slight pause helps media finish and save video correctly
            if UIVideoAtPathIsCompatibleWithSavedPhotosAlbum((self.vc.filePath?.relativePath)!) {
                UISaveVideoAtPathToSavedPhotosAlbum((self.vc.filePath?.relativePath)!, nil, nil, nil)
            }else{
                print("error could not save")
            }
        }
        vc.cameraSession.beginConfiguration()
        vc.cameraSession.removeOutput(vc.videoFileOutput)
        vc.cameraSession.commitConfiguration()

    }

This is my code and I know that the only line that runs is the self.vc.videoFileOutput.stopRecording(). I do not know why this is the only line that runs, but the main purpose is to run the UISaveVideoAtPathtoSavedPhotosAlbum line. I have tried running this in the applicationWillResign, but it still only stops the recording.