docker-compose.yml

version: '3'
services:
  db:
    image: postgres:11.3

    environment:
      - POSTGRES_DB=maestro
      - POSTGRES_USER=lucky
      - POSTGRES_PASSWORD=developer
    ports:
      - 5432:5432
    volumes:
      - data:/var/lib/postgresql/data

  app:
    build: .
    image: maestro
    command: /app/bin/maestro
    environment:
      - DATABASE_URL=postgres://lucky:developer@db:5432/maestro
      - DB_HOST=db
      - DB_USERNAME=lucky
      - DB_PASSWORD=developer
    ports:
      - 3000:3000
    links:
      - db
    volumes:
      - .:/app
      - nodes:/app/node_modules
      - shards:/app/lib
    depends_on:
      - db

volumes:
  data:
  nodes:
  shards:

Dockerfile

FROM crystallang/crystal:latest

WORKDIR /app

COPY shard.* /app/
RUN shards install
COPY . /app
RUN crystal build src/maestro.cr -o ./bin/maestro --release

RUN rm -rf /app/node_modules