Pyqt5 crashing program with QThread function

Question

class Thread1(QtCore.QThread):
    def __init__(self):
        super().__init__()

    def run(self) -> None:
        with sr.Microphone() as source:
            audio = r.listen(source)
        try:
            print("You said " + r.recognize_google(audio))
        except LookupError:
            print("Could not understand audio")

class MainWindow(QMainWindow):

    def __init__(self):
        QMainWindow.__init__(self)
        pybutton = QPushButton('Click me', self)
        pybutton.clicked.connect(self.clickMethod)
        pybutton.resize(100,32)
        pybutton.move(50, 50)

    def clickMethod(self):
        Thread1().start()

if __name__ == "__main__":

    app = QtWidgets.QApplication(sys.argv)
    mainWin = MainWindow()
    mainWin.show()
    sys.exit(app.exec_())

If i call this function program is crashing but if i call in debug mode code is working. What's the wrong here?