配置react-router-dom会生成一个错误: Invariant :您不应该在<Router>外部使用<Link>

import React from 'react';
import { BrowserRouter as Router, Link, Route } from 'react-router-dom';

const App = () => {
  return (
    <Router>
      <div>
        <nav>
          <ul>
            <li>
              <Link to="/">Home</Link>
            </li>
            <li>
              <Link to="/about">About</Link>
            </li>
            <li>
              <Link to="/contact">Contact</Link>
            </li>
          </ul>
        </nav>

        <Route path="/" exact component={Home} />
        <Route path="/about" component={About} />
        <Route path="/contact" component={Contact} />
      </div>
    </Router>
  );
};

const Home = () => {
  return <h1>Home</h1>;
};

const About = () => {
  return <h1>About</h1>;
};

const Contact = () => {
  return <h1>Contact</h1>;
};

export default App;