Docker-compose Postgres connection refused

I'm running Postgres DB with pg-admin and GO on the docker-compose.

Problem: I can connect from pg-admin to Postgres. But cannot establish a connection from Go.

I tried different combinations of authentication string but it does not work. String format same as here https://github.com/karlkeefer/pngr - but different container name - database

(ERROR) Connection URl:

backend_1         | 2021/08/08 14:24:40 DB connection: database://main:fugZwypczB94m0LP7CcH@postgres:5432/temp_db?sslmode=disable
backend_1         | 2021/08/08 14:24:40 Unalble to open DB connection: dial tcp 127.0.0.1:5432: connect: connection refused

(URI generation same as here https://github.com/karlkeefer/pngr)

Docker:

version: '3.8'
services:
  backend:
    restart: always
    build: 
      context: backend
      target: dev
    volumes:
      - ./backend:/root
    ports:
      - "5000:5000"
    env_file: .env
    depends_on: 
      - database
  database:
    build: database
    restart: always
    environment:
      POSTGRES_DB: ${POSTGRES_DB}
      POSTGRES_USER: ${POSTGRES_USER}
      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
      PGDATA: /var/lib/postgresql/data
    volumes:
      - ./database/data:/var/lib/postgresql/data
      - ./logs/databse:/var/log/postgresql
      - ./database/migrations:/docker-entrypoint-initdb.d/migrations
    ports:
      - "5432:5432"
  database-admin:
    image: dpage/pgadmin4:5.5
    restart: always
    environment:
      PGADMIN_DEFAULT_EMAIL: ${PG_ADMIN_EMAIL}
      PGADMIN_DEFAULT_PASSWORD: ${PG_ADMIN_PASSWORD}
      PGADMIN_LISTEN_PORT: 80
    ports:
      - "8080:80"
    volumes:
      - ./database/admin:/var/lib/pgadmin
    links:
      - "database:pgsql-server"
    depends_on: 
      - database
volumes:
  database:
  database-admin:

Environment:

POSTGRES_HOST=postgres
POSTGRES_PORT=5432
POSTGRES_DB=temp_db
POSTGRES_USER=main
POSTGRES_PASSWORD=fugZwypczB94m0LP7CcH
PG_ADMIN_EMAIL=admin@temp.com
PG_ADMIN_PASSWORD=ayzi2ta8f1TnX3vKQSN1
PG_ADMIN_PORT=80

GO Code:

db, err = sqlx.Open("postgres", str)

str

func buildConnectionString() string {
	user := os.Getenv("POSTGRES_USER")
	pass := os.Getenv("POSTGRES_PASSWORD")
	if user == "" || pass == "" {
		log.Fatalln("You must include POSTGRES_USER and POSTGRES_PASSWORD environment variables")
	}
	host := os.Getenv("POSTGRES_HOST")
	port := os.Getenv("POSTGRES_PORT")
	dbname := os.Getenv("POSTGRES_DB")
	if host == "" || port == "" || dbname == "" {
		log.Fatalln("You must include POSTGRES_HOST, POSTGRES_PORT, and POSTGRES_DB environment variables")
	}

	str := fmt.Sprintf("database://%s:%s@%s:%s/%s?sslmode=disable", user, pass, host, port, dbname)

	log.Println("DB connection: " + str)

	return str
}

Thanks in advance!

You reference the database hostname as postgres (POSTGRES_HOST=postgres) which is fine, but the container/service name is database.

Either change the name in your compose.yaml from database to postgres or add an explicit hostname field:

database:
  build: database
  restart: always
  hostname: postgres   # <- add this

You may also want to add a dedicated network for multiple container services to talk to one another (or prevent others from). To do this, add this to each service your want to use a specific network e.g.

database:
  # ...

  networks:
    - mynet

backend:
  # ...

  networks:
    - mynet

and define the network at the end of your compose.yaml

networks:
  mynet:
    name: my-shared-db-network