title: Can't set Password for Postgres using docker-compose
body: <p>I am not able to set Password for Postgres using Docker-compose. Postgres is loading without password and with the default user name "postgres", non of the environment variables below seems to applied. below is the db service of my docker-compose.yml file: (version 3)</p>
  
  <pre><code>db:
    image: postgres
    container_name: postgres
    environment:
        POSTGRES_USER: user
        POSTGRES_PASSWORD: pass
        POSTGRES_DB: db
    restart: unless-stopped
    volumes:
      - ./postgres-data:/var/lib/postgresql/data
    ports:
      - "5432:5432"
  </code></pre>
  
  <p>Note I tried using the "-POSTGRES_USER=" as well, it didn't work</p>
  
  <p>Also, I deleted all old containers/volumes.</p>
  
  <p>Any idea?</p>