How to update state using setInterval on functional components in React

Question

I am trying to implement a countdown, but the state is not being update as expected. It stays stuck on initial value 30. I have no clue how to solve it. Can anyone help me please?

  const [timer, setTimer] = useState(30);

  function handleTimer() {
    const interval = setInterval(() => {
      setTimer((count) => count - 1);
      if (timer <= 0) {
        clearInterval(interval);
      }
    }, 1000);
  }

  useEffect(() => {
    handleTimer();
  }, []);