title: How to set up graphql-upload with koa-graphql?
body: <p>Currently using koa-graphql to set up a graphql server with koa router, attempting to connect graphql-upload to it so I can upload files, however I'm getting an empty object when sending a file through a mutation</p>
  <p>server.js</p>
  <pre><code>import '@babel/polyfill';
  import Koa from 'koa';
  import bodyParser from 'koa-bodyparser';
  import Router from 'koa-router';
  import graphqlHTTP from 'koa-graphql';
  import schema from './../graphql/schema';
  import rootValue from './../graphql/resolvers/index';
  
  const port = parseInt(process.env.PORT, 10) || 3000;
  
  const server = new Koa();
  const router = new Router();
  server.use(bodyParser({jsonLimit: '50mb'})); 
  router.all('/graphql', graphqlHTTP({schema, rootValue}));
  server.use(router.allowedMethods());
  server.use(router.routes());
  server.listen(port, () =&gt; console.log(`Running on PORT ${port}`));
  </code></pre>
  <p>schema.js</p>
  <pre><code>import {buildSchema} from 'graphql';
  
  export default buildSchema(`
    scalar Upload
  
    type Obj {
      _id: ID!
      image: String!
      title: String!
    }
  
    type RootQuery {
      objs: [Obj]!
    }
  
    type RootMutation {
      createObj(obj: ObjInput!): String!
    }
  
    input ObjInput {
      title: String!
      image: Upload!
    }
  
    schema {
      query: RootQuery
      mutation: RootMutation
    }
  `);
  </code></pre>
  <p>resolvers</p>
  <pre><code>import rootQuery from './query';
  import rootMutation from './mutations';
  import {GraphQLUpload} from 'graphql-upload';
  
  export default {
    Upload: GraphQLUpload,
    ...rootQuery,
    ...rootMutation
  };
  </code></pre>
  <p><a href="https://www.npmjs.com/package/koa-graphql" rel="nofollow noreferrer">https://www.npmjs.com/package/koa-graphql</a></p>
  <p><a href="https://www.npmjs.com/package/graphql-upload" rel="nofollow noreferrer">https://www.npmjs.com/package/graphql-upload</a></p>