sudo docker build -t PROJECT_NAME .

db:
    image: mysql
    restart: always
    ports:
      - "8999:3306"
    networks:
      - webnet
    environment:
      MYSQL_DATABASE: slack
      MYSQL_ROOT_PASSWORD: admin

Unhandled rejection SequelizeConnectionRefusedError: connect ECONNREFUSED 172.18.0.4:3306

const sequelize = new Sequelize(process.env.TEST_DB || process.env.MYSQL_DATABASE, 'root', 'admin', {
  host: process.env.DB_HOST || 'localhost',
  operatorsAliases: Sequelize.Op,
  dialect: 'mysql',
  define: {
    underscored: true
  }
});

web:
    image: slack-clone-server
    ports:
      - "8080:8080"
    networks:
      - webnet
    environment:
      DB_HOST: db
      REDIS_HOST: redis
    command: ["./wait-for-it.sh", "db:3306", "--", "npm", "run", "prod"]