useSWR mutate function not working as expected - reactjs

Question

mutate function not working as i expected, when sharing same state with other components
expect:
every mutate call by clicking button, re-fetch original data, so i can find new post.json request on networkTab
working: but, every mutate call, not fetch new data. i couldn't find post.json on networkTab
if i remove Item.js file, it works as i expected.(every mutate-call, every re-fetch)
why this happening?
//App.js
import React from 'react';
import logo from './logo.svg';
import './App.css';
import useSWR from 'swr'
import ItemList from './ItemList';
function App() {
React.useEffect(()=>{
console.log('rerender')
})
const fetcher = async(urlKey) => {
const url = 'https://jsonplaceholder.typicode.com/posts';
const response = await fetch(url);
const result = await response.json();
return result
}
const {data,error,mutate} = useSWR('/get/posts',fetcher);
const updateFetch = () => {
mutate({},true);
}
return (
<div className="App">
<ItemList/>
<button onClick={updateFetch}>reFresh</button>
</div>
);
}
export default App;
//ItemList.js
import React from 'react'
import useSWR from 'swr';
function ItemList() {
const {data,error} = useSWR('/get/posts');
return null
}
export default ItemList

Answer 1

According to docs:
broadcast a revalidation message globally to other SWR hooks using the same key by calling mutate(key).
i.e You have to tell mutate which Api data you have to fetch again in your case. It would be like this:
mutate('/get/posts',true)
I have created this sandbox for reference: https://codesandbox.io/embed/reverent-cloud-fhm2w