The button doesn't work in SpeechKit / swift

Question

You can find my code below. I wrote code, where I can recognise my speech and prevent it into text. But unfortunately this code works only once, when I need to add recognise my speech again I should to restart the app or a viewController. So I have a question: how should I change my code, if I need to recognise my speech every time I push the button and call the function without restarting the app.

This is function code:

func recordAndRecognizeSpeech() {
    let node = audioEngine.inputNode
    let recordingFormat = node.outputFormat(forBus: 0)
    node.installTap(onBus: 0, bufferSize: 1024, format: recordingFormat) { buffer, _ in
        self.request.append(buffer)
    }
    audioEngine.prepare()
    do {
        try audioEngine.start()
    } catch {
        return print(error)
    }
    guard let myRecognizer = SFSpeechRecognizer() else {
        return
    } 
    if !myRecognizer.isAvailable {
        return
    }
    recognitionTask = speechRecognizer?.recognitionTask(with: request, resultHandler: { [weak self] result, error in
        if let result = result {
            let bestString = result.bestTranscription.formattedString
            self?.recognizedLabel.text = bestString
        } else if let error = error {
            print(error)
        }
    })
}

This is button code:

@IBAction func micBtnTouchDown(_ sender: Any) {
    self.recordAndRecognizeSpeech()
}

Thank you, and have a nice day!