I'm trying to use docker for a firebase project, for firebase the `package.json` is in a sub folder called functions. I'm using the node:alpine image.

In my Dockerfile, I need to cd into the functions directory then run `npm run start`. How do I do this, please?

I have tried CMD [ "cd", "functions", ";", "npm", "run", "serve" ], I got this error `/usr/local/bin/docker-entrypoint.sh: exec: line 8: cd: not found`

```
FROM node:alpine

WORKDIR '/app'

RUN npm install -g firebase-tools

COPY functions/package*.json functions/

RUN cd functions && npm install && cd ..

COPY . .

CMD [ "cd", "functions", ";", "npm", "run", "serve" ]

```