I got an error "Must provide query string."
I want to upload an image, but I got an error
```json
{
  "errors": [
    {
      "message": "Must provide query string."
    }
  ]
}
```
My code:

**UploadFile.js**
```js
import { GraphQLUpload } from 'graphql-upload';
import fetch from 'node-fetch';
import config from 'config';
import awaitWrap from 'utils/promise';
import domain from 'utils/domain';

export const schema = [
  `
  type UploadImageResponse {
    code: String!
    message: String!
    data: String
  }
`,
];

export const mutation = [
  `
  # upload image
  imageUpload(
    type: Int!

    # file
    file: Upload!
  ): UploadImageResponse
`,
];

// 
const url = `${config.api.cmsUrl}/web/upload`;

export const resolvers = {
  Upload: GraphQLUpload,
  Mutation: {
    async imageUpload({ request }, args) {
      console.info('----', args);
      const { session, hostname } = request;

      const { type, file } = args;
      const { filename, mimetype } = await file;
      const fetchUrl = url;

      console.info('mimetype', mimetype, args);
      if (!/image/.test(mimetype || '')) {
        console.info('Upload file not Image', filename);
        return {
          code: 405,
          message: 'error',
          data: '',
        };
      }

      const token = (session.user && session.user.accessToken) || '';

      const formData = new FormData();
      formData.append('file', file);
      formData.append('hostname', domain(hostname));
      formData.append('type', type);

      const [error, response] = await awaitWrap(
        fetch(fetchUrl, {
          method: 'POST',
          body: formData,
          headers: {
            'Content-Type': 'multipart/form-data',
            Authorization: token,
          },
          timeout: config.timeout,
        }),
      );

      if (error) {
        return {
          code: 500,
          message: error.message,
        };
      }

      const result = await response.json();
      console.info('result', result);

      const { code, data, msg } = result;

      if (code === '800401' || code === '80410') request.session.user = null;

      return { code, data, message: msg };
    },
  },
};

```
**UploadFile.graphql**
```graphql
mutation uploadFile($size: Int!, $file: Upload!) {
  uploadFile(size: $size, file: $file) {
    code
    message
    url
  }
}

```

Chrome Console Output
![image](https://user-images.githubusercontent.com/8652062/81277577-2c832b80-9087-11ea-864e-4f6386054454.png)

I don't know what the problem is，I hope someone can help me.
Thanks a lot.

