POSTGRES_DB: customer in compose.yml

[hazartilirot]

Basically, if you open the official docker postgres page there would be the subject's description.
You just need to add this line to your compose.yml file in order to create the default database customer
POSTGRES_DB: customer

version: "3.9"

services:
  db:
    container_name: postgres
    image: postgres:latest
    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: root
      POSTGRES_DB: customer
      PGDATA: /data/postgres
    volumes:
      - db:/data/postgres
    ports:
      - 5432:5432
    networks:
      - db
    restart: unless-stopped

networks:
  db:
    driver: bridge
volumes:
  db: