How to Avoid Errors When Using Swift to Run SFSpeakRecognizer and AVSpeechSynthsizer in One App

private func startRecording()throws{
    // Describe the action to record here
    iflet recognitionTask = recognitionTask {
        // reset processing
        recognitionTask.cancel()
        self.recognitionTask=nil
        let audioSession=AVAudioSession.sharedInstance()
        try audioSession.setCategory (AVAudioSession.Category.record, mode:.default)
        try audioSession.setMode (AVAudioSession.Mode.measurement)
        tryaudioSession.setActive(true, options: .notifyOthersOnDeactivation)
    }
}

vartalker=AVSpeechSynthsizer()

override func viewDidLoad(){
    // speechButton generation process
    speechButton.addTarget(resultCardView, action:#selector(speachButtonTapped(sender:))), for: .touchUpInside 
}

@objc func speachButtonTapped(sender:Any){
    let avSession=AVAudioSession.sharedInstance()
    try?avSession.setCategory(AVAudioSession.Category.ambient, mode: .default, options: .mixWithOthers)
    letutterance=AVSpeechUtterance(string:self.Jplabel.text!)
    utterance.voice = AVSpeechSynthesisVoice (language: "en-En")
    utility.volume=1.2
    // execution
    self.talker.speak (utterance)
}