docker-compose.yaml

# version: "3.9"

services:
  postgres:
    image: postgres:12-alpine # user pre-built docker image
    environment: # to specify env var
      - POSTGRES_USER=root
      - POSTGRES_PASSWORD=secret
      - POSTGRES_DB=simple_bank

  api:
    # Defines the API service for handling requests to Simple Bank
    build:
      # Build the Go application into a Docker image using Dockerfile in the current directory
      context: . # specify context to build the img, current root folder
      dockerfile: Dockerfile # where to find Dockerfile to build the img
    ports:
      # Publish container port 8080 to host port 8080, so external clients can reach the API (from outside of container)
      - "8080:8080"
    environment:
      - DB_SOURCE=postgresql://root:secret@postgres:5432/simple_bank?sslmode=disable
      # Connection string for PostgreSQL; overrides any default in app.env
      # All services in docker-compose will run on the same network.
      # Services on the same Docker network can refer to each other by name (here, "postgres").
    depends_on:
      # start the server only after postgres is ready
      # otherwise the server exit immediately (since it cannot connect to db)
      - postgres
    entrypoint: [ "/app/wait-for.sh", "postgres:5432", "--", "/app/start.sh" ]
    command: [ "/app/main" ]