title: Next.js getInitialProps context query is empty
body: <p>I'm following this basic <a href="https://nextjs.org/learn/basics/fetching-data-for-pages/fetching-data-for-pages" rel="nofollow noreferrer">tutorial</a> about Next.js.</p>
  
  <p>They provide this code:</p>
  
  <pre><code> Post.getInitialProps = async function(context) {
    const { id } = context.query;
    const res = await fetch(`https://api.tvmaze.com/shows/${id}`);
    const show = await res.json();
  
    console.log(`Fetched show: ${show.name}`);
  
    return { show };
  };
  </code></pre>
  
  <p>which I have copy-pasted. However context.query is an empty object, so, my api call is failing.
  Here's the code from wehre I'm redirecting to that dynamic page (pages/p/[id].js)</p>
  
  <pre><code> &lt;Layout&gt;
  &lt;h1&gt;Batman TV Shows&lt;/h1&gt;
  &lt;ul&gt;
    {props.shows.map(show =&gt; (
      &lt;li key={show.id}&gt;
        &lt;Link href="/p/[id]" as={`/p/${show.id}`}&gt;
          &lt;a&gt;{show.name}&lt;/a&gt;
        &lt;/Link&gt;
      &lt;/li&gt;
    ))}
  &lt;/ul&gt;
  
  
  &lt;/Layout&gt;
  </code></pre>
  
  <p>is this a bug, or am I missing something?</p>