how to use useParams inside a ContextProvider

I have something like this

return (
    <Router>
      <MyContextProvider>
        <Routes>
          <Route path="/" ...
          <Route path="/posts/:slug" ...

return (
    <Router>
      <MyContextProvider>
        <Routes>
          <Route path="/" ...
          <Route path="/posts/:slug" ...

return (
    <Router>
      <MyContextProvider>
        <Routes>
          <Route path="/" ...
          <Route path="/posts/:slug" ...

return (
    <Router>
      <MyContextProvider>
        <Routes>
          <Route path="/" ...
          <Route path="/posts/:slug" ...

and I want to access the slug on MyContextProvider on inital page load.

useParams seems to always return an empty object