Gorm application fails to connect to PostgreSQL in docker container on Mac, ignores DSN

I tried creating a simple go rest api. I use the Gorm library for DB handling, but it fails connecting to the DB in the container. I feel like this could be an issue of Docker on Apple silicon, but not sure. I have another project, which uses basically the same setup, but there's no problem with DB connections at all.

Basically the connection parameters seem to change completely at runtime ignoring the DSN string

Here's the docker-compose.yml:

version: '3'

services:
  db:
    image: 'postgres:latest'
    container_name: bazos-watcher-db
    ports:
      - '5420:5432'
    volumes:
      - dbdata:/var/lib/postgresql/data
      - ./scripts/init.sql:/docker-entrypoint-initdb.d/init.sql
    env_file:
      - 'docker.env'
    restart: always

volumes:
  dbdata:

Here's the part that does the DB connection:

dsn := "bazos:kokos@tcp(localhost:5420)/bazos?charset=utf8mb4&parseTime=True&loc=Local"

dbOpen, err := gorm.Open(postgres.Open(dsn), &gorm.Config{})

The DSN parameters match those configured in docker.env. pgAdmin has no problem making a connection.

Here's the error I get, the connection parameters seem change completely for some reason:

[error] failed to initialize database, got error failed to connect to `host=/private/tmp user=tassilo database=`: dial error (dial unix /private/tmp/.s.PGSQL.5432: connect: no such file or directory)
2023/03/15 17:20:59 failed to connect to `host=/private/tmp user=tassilo database=`: dial error (dial unix /private/tmp/.s.PGSQL.5432: connect: no such file or directory)
exit status 1

I have tried changing the last part of the DSN string and deleting and recreating the container but still no success.

I believe your problem is with @tcp(localhost:5420) - in Docker, your database service is specified as db and so your dsn should be @tcp(db). You may also need to specify the local driver in your docker compose:

volumes:
  dbdata:
    driver: local

I naively assumed the format for DSN string is the same as for MySQL. Instead it should look like this:

dsn := "host=localhost user=gorm password=gorm dbname=gorm port=9920 sslmode=disable TimeZone=Asia/Shanghai"

1. first shutdown running database service

docker-compose down db

2. Update the compose file with network_mode parameter as below

    version: '3'
    
    services:
      db:
        image: 'postgres:latest'
        container_name: bazos-watcher-db
        network_mode: "host"
        ports:
          - '5420:5432'
        volumes:
          - dbdata:/var/lib/postgresql/data
          - ./scripts/init.sql:/docker-entrypoint-initdb.d/init.sql
        env_file:
          - 'docker.env'
        restart: always
    
    volumes:
      dbdata:

3. Run your db service in detached mode with -d option

docker-compose up db -d

4. update your dsn string with below ( do not forget to put your db password )

    dsn := "host=localhost user=bazos password=<YOUR PASSWORD> dbname=bazos port=5420 sslmode=disable"

    dbOpen, err := gorm.Open(postgres.Open(dsn), &gorm.Config{})

I hope it would work.