title: Unable to use rocket::serde::json::Json despite both rocket and serde listed as dependencies
body: <p>I followed the <a href="https://rocket.rs/v0.5-rc/guide/getting-started/" rel="nofollow noreferrer">quickstart guide</a>. Now I'm trying to return some super simple JSON and the documentation is wrong and there's no way to submit a ticket without getting on IRC.</p>
  <h2>Error</h2>
  <pre class="lang-sh prettyprint-override"><code>error[E0432]: unresolved import `rocket::serde::json`
   --&gt; src/main.rs:2:20
    |
  2 | use rocket::serde::json::Json;
    |                    ^^^^ could not find `json` in `serde`
  
  For more information about this error, try `rustc --explain E0432`.
  error: could not compile `my-api` due to previous error
  </code></pre>
  <h1>Files</h1>
  <p><code>Cargo.toml</code></p>
  <pre><code>[package]
  name = &quot;my-api&quot;
  version = &quot;0.1.0&quot;
  edition = &quot;2021&quot;
  publish = false
  
  # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
  
  [dependencies]
  rocket = &quot;0.5.0-rc.1&quot;
  serde = &quot;1.0.130&quot;
  </code></pre>
  <p><code>main.rs</code></p>
  <pre class="lang-rust prettyprint-override"><code>#[macro_use] extern crate rocket;
  use rocket::serde::{Serialize, json::Json};
  
  #[derive(Serialize)]
  struct Location {
      lat: String,
      lng: String,
  }
  
  #[get(&quot;/?&lt;lat&gt;&amp;&lt;lng&gt;&quot;)]
  fn location(lat: &amp;str, lng: &amp;str) -&gt; Json&lt;Location&gt; {
      Json(Location {
          lat: 111.1111.to_string(),
          lng: 222.2222.to_string(),
      })
  }
  
  #[launch]
  fn rocket() -&gt; _ {
      rocket::build().mount(&quot;/&quot;, routes![location])
  }
  </code></pre>
  <p>If you go <a href="https://rocket.rs/v0.5-rc/guide/responses/#json" rel="nofollow noreferrer">here</a> you'll see this is almost a direct copy/paste from the documentation. I don't know enough of Rust to troubleshoot dependency errors.</p>