How do volumes work on app engine?

[Samuel Navarro]

I have a production angular application inside a docker image. When I deploy to app engine I re-use that image. I'm attempting to replace a file inside my assets folder WHEN the image is deploy (which is when at some point app engine runs docker run ... ).

On a regular docker installation i would just mount a volume from the host machine to the assets folder in the container.

Reading the docs it seems I can add a volume on the app.yaml, and that volume always reads to /mnt/NAME. 

1) How can I send a file to app engine to be included in the volume that will be mounted to the container?