Issue with uploading PDF to S3 with apollo-server-lambda
I try to upload a pdf file to S3, and files are uploading, but files have blank pages or are even not open.

I tried to apply the same logic with uploading on the express server without the serverless framework, and it works. 
I don't understand how I should upload my pdf's to S3 from apollo-server-lambda serverless server, 
So maybe you can help with some tip

Here is my code, how i run the server:
```javascript
export const handler = server.createHandler({
  expressAppFromMiddleware(middleware) {
    const app = express();
    app.use(graphqlUploadExpress());
    app.use(middleware);
    return app;
  },
})
```

Here is my code, how i save the file to S3:
```javascript
const createUploadStream = (key) => {
  const pass = new stream.PassThrough();
  return {
    writeStream: pass,
    promise: s3
      .upload({
        Bucket: 'my-bucket',
        Key: key,
        Body: pass
      })
      .promise()
  };
}

const resolvers = {
  Upload: GraphQLUpload,
  Mutation: {
    singleUpload: async (parent, { file }) => {
      const { createReadStream, filename, mimetype, encoding } = await file;
      const stream = createReadStream()

      const filePath = filename

      const uploadStream = createUploadStream(filePath);

      stream.pipe(uploadStream.writeStream);

      const result = await uploadStream.promise;

    },
  },
};
```