avcapturedevice - 当应用程序进入后台时，如何保持我的闪光灯代码运行？

Question

Button(action: {
    DispatchQueue.global(qos: .userInteractive).async {
        self.lightOn.toggle()
        
        let cam = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .back)
        
        try? cam?.lockForConfiguration()
        
        if (cam?.torchMode == AVCaptureDevice.TorchMode.on) {
            cam?.torchMode = AVCaptureDevice.TorchMode.off
        }
        else if value == 0.0 {
            do {
                try cam?.setTorchModeOn(level: 0.05)
            }
            catch {
                print(error)
            }
        }
        else  {
            do {
                try cam?.setTorchModeOn(level: value)
            }
            catch {
                print(error)
            }
        }
        
        cam?.unlockForConfiguration()
    }
})

我试过gos:.userInteractive, userInitiated，utilities但background它似乎不起作用。任何人都可以让我知道出了什么问题？