When I take docker containers down and up again, my MongoDB collections are all gone. 

* I run `docker-compose up` and add a new database, collection, and document.
* I then run `docker-compose down` and then `docker-compose up`.
* Data is gone.

It works fine if I am just stopping and starting the containers though. My host machine is macOS Mojave 10.14 with Docker Desktop 2.1.

I have the following docker-compose.yaml version 3.4 file:

```
  mongodb:
      image: mongo:4.2.1
      volumes:
           - ./docker/data/mongodb:/var/lib/mongodb:rw
      ports:
      - target: 27017
        published: 27018
        protocol: tcp

```

I am not sure what I am doing wrong with the volume mounts. When I look on my host machine at ./docker/data/mongodb nothing is being written to it, ever. I went ahead and set permissions to 777 on that to see if it was a permissions issue, hail mary, I know.