version: '2'
services:
    postgres:
        image: postgres
        environment:
            POSTGRES_PASSWORD: '...'
            POSTGRES_USER: '...'
            POSTGRES_DB: '...'
    web:
        build: .
        command: rails s -b '0.0.0.0' -p 4000
        ports:
            - "4000:4000"
        depends_on:
            - postgres
        environment:
            DATABASE_URL: postgres://<user>@postgres/<table>