If you look at the location bar of the browser when you visit the second page, you'll see something like http://localhost:3000/second?id=0, which is fine, but not pretty enough. We can add some niceness to the URL schema that we use. This is optional, but it's always good to have SEO-friendly URLs instead of query-string parameters.
In order to do that, we should use a special as prop of the Link component:
<Link as={`/post/${index}`} href={{pathname: '/second', query: {id: index}}}>
<a>{post.title}</a>
</Link>
But, if you visit such a link and reload the page, you will see 404 Page Not Found error. Why is that? It's because URL masking (a technology we just used) works on the client side at runtime, and when we reload the page we need to teach the server to work with such...
