Why server get upload.file.stream of undefined
client send a graphql like this:
![image](https://user-images.githubusercontent.com/14294893/39528790-a6244948-4e57-11e8-89ad-fc2f7f57f420.png)
and the image msg like this:
![image](https://user-images.githubusercontent.com/14294893/39528867-df3c7e6c-4e57-11e8-9842-6199f73bf1e1.png)
but the server get the file only has a uid props after used 'apollo-upload-server'
![image](https://user-images.githubusercontent.com/14294893/39528986-296363fc-4e58-11e8-82f7-09e63cf28c56.png)
but your demo has got the props(stream, filename, mimetype, encoding) in file prop.

why i cannot get those props in file prop
