version: "3.7"

services:
  pg:
    image: postgres:12.1
    # The `always` option below will make sure this
    # container is started when you turn on your machine,
    # so you don't have to worry about it everytime.
    restart: always
    ports:
      # The 127.0.0.1 prefix makes sure this instance
      # cannot be accessed externally, so it is ok
      # for this instante to have no password.
      - "127.0.0.1:5432:5432"
    environment:
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=postgres