title: Unknown type "Upload" in Apollo Server 2.6
body: <p>I want to upload a file through GraphQL, and followed this <a href="https://blog.apollographql.com/file-uploads-with-apollo-server-2-0-5db2f3f60675" rel="nofollow noreferrer">article</a>.</p>
  
  <p>Here's the my schema:</p>
  
  <pre><code>extend type Mutation {
    bannerAdd(
      title: String!
      image: Upload
    ): ID
  }
  </code></pre>
  
  <p>However when I run the app, this gives me this error:</p>
  
  <blockquote>
    <p>Unknown type "Upload". Did you mean "Float"?</p>
  </blockquote>
  
  <p>Followed above article, Apollo Server will automatically generate Upload scalar, but why this is happening?</p>
  
  <p>Also define Upload scalar manually also not working:</p>
  
  <pre><code>scalar Upload
  
  ...
  </code></pre>
  
  <p>Gives me this error:</p>
  
  <blockquote>
    <p>Error: There can be only one type named "Upload".</p>
  </blockquote>
  
  <p>Seems nothing wrong with my code. Is there an anything that I missed? Using Node@10.14.2, Apollo Server@2.6.1, Apollo Server Express@2.6.1 and polka@0.5.2.</p>
  
  <p>Any advice will very appreciate it.</p>