如何用hooks实现componentWillMount

https://codesandbox.io/s/heuristic-lamport-xzzmh?file=/src/App.js

const useWillMount = (fn) => {
  const willMount = useRef(true);
  useEffect(() => {
    willMount.current = false;
  }, []);
  if (willMount.current) {
    fn && fn();
  }
};