docker-compose.yml

version: "3.5"
services:
  nest:
    container_name: nest-api
    build:
      context: .
      target: development
    command: npm run start:dev
    env_file:
      - .env
    ports:
      - 3000:3000
    volumes:
      - .:/usr/src/app
      - /usr/src/app/node_modules
    depends_on:
      - postgres
  postgres:
    container_name: pg
    image: postgres:9.6.15
    environment:
      PGDATA: /var/lib/postgresql/data/pgdata
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: postgres
    volumes: 
      - ./docker-entrypoint-initdb.d:/docker-entrypoint-initdb.d
      - ./pgdata:/var/lib/postgresql/data
    ports:
      - 5432:5432
networks:
  default:
    name: webapp

Dockerfile

FROM node:12.16.1 As development
WORKDIR /usr/src/app
COPY package*.json ./
RUN npm install --only=development
COPY . .
RUN npm run build

ormconfig.js

const ENV = process.env.NODE_ENV || 'development';

const defaultConfig = {
  type: 'postgres',
  host: 'postgres',
  username: 'postgres',
  password: 'postgres', 
  database: 'roomates-dev',
  migrationsRun: true,
  entities: ['dist/**/*.entity.{ts,js}'],
  migrations: ['dist/migrations/*.{ts,js}'],
  cli: {
    migrationsDir: 'src/migrations'
  },
};

// TypeORM config for production
if (ENV === 'production') {
  module.exports = Object.assign(defaultConfig, {
    host: process.env.POSTGRES_HOST,
    username: process.env.POSTGRES_USER,
    password: process.env.POSTGRES_PASSWORD,
    database: process.env.POSTGRES_DATABASE,
    migrationsRun: false,
  });
}

// TypeORM config for development
if (ENV === 'development') {
  module.exports = defaultConfig;
}