Why is my Go application refusing a connection to my Docker Compose Postgres database, despite pgAdmin connecting successfully?

Docker-Compose Postgres Connection Refused: Resolving the Connection Issue

In a Docker-Compose setup with Postgres, you described an issue where you can connect to Postgres using pg-admin but face a connection issue when attempting to connect from Go.

The problem stems from the way you reference the database hostname in your Go code. You are using POSTGRES_HOST as postgres, which is the container/service name for Postgres in your Docker-Compose configuration. However, in your Go code, you are connecting to database, which is the actual container name for the database service.

To resolve this issue, you have two options:

Option 1: Change Container Name in Docker-Compose

Change the name of your database service in your docker-compose.yaml file from database to postgres. This will make the container name and the hostname you are using in your Go code match.

Option 2: Explicit Hostname Field

Alternatively, you can add an explicit hostname field to the database service in your Docker-Compose configuration:

database:
  build: database
  restart: always
  hostname: postgres

This sets the hostname of the database container to postgres, which matches the hostname you are referencing in your Go code.

Additional Considerations

Additionally, you may want to consider creating a dedicated network within your Docker-Compose configuration to ensure that containers can communicate with each other securely and efficiently. Here's how to do it:

In your docker-compose.yaml file, add a networks section to each service that should use the dedicated network, like this:

database:
  # ...

  networks:
    - mynet

backend:
  # ...

  networks:
    - mynet

Then, define the network at the end of your docker-compose.yaml file:

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

This will create a new network named my-shared-db-network that your containers can use to communicate.

By implementing one of these solutions, you should be able to successfully connect to your Postgres database from Go within your Docker-Compose setup.

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