[Python] Exit() from background function fails in Python [duplicate]

I'm learnig python and doing some simple programming exercises (Python 3.13.2 and VScode 1.97.1)
Here, while a counter runs in the while loop, I'm listening for any key press in the background.
When "z" is pressed the counter should be set to 0, and when"q" is pressed, the program should exit.
Debugging the program, the key press listener is working and checking the keys correctly.
But the sys.exit() function doesn't work. The counter still keeps on counting.
Where am I going wrong?

import sys
from time import sleep
import os
from pynput.keyboard import Key, Listener

def cls(): # clear terminal screen, cross-platform
os.system('cls' if os.name=='nt' else 'clear')

cnt = 1
def checkKey(key): # is called, when a key is pressed
if hasattr(key, 'char'):
if key.char == 'z':
global cnt
cnt = 0
if key.char == 'q':
sys.exit() # is not quitting the program
pass

# Non-Blocking Listener
listener = Listener(on_press=checkKey)
listener.start()

cls()
sleep(0.5)


while True:
print("{0}".format(cnt), end='\r', flush=True) # print n in the same line, without carriage return and deactivated output buffer
sleep(0.5)
cnt += 1

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