@IBAction func lightButtonClick(_ sender: UIButton) {
        let device = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
        if device == nil {
            sender.isEnabled = false
            return
        }
        if device?.torchMode == AVCaptureTorchMode.off{
            do {
                try device?.lockForConfiguration()
            } catch {
                return
            }
            device?.torchMode = .on
            device?.unlockForConfiguration()
            sender.isSelected = true
        }else {
            do {
                try device?.lockForConfiguration()
            } catch {
                return
            }
            device?.torchMode = .off
            device?.unlockForConfiguration()
            sender.isSelected = false
        }
    }