Job failing to connect to server

Working on a project in DRF. I have two databases; local PostgreSQL DB as default, and SQLite3 for testing.

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': DB_NAME,
        'USER': DB_USERNAME,
        'PASSWORD': DB_PASSWORD,
        'HOST': DB_HOST,
        'PORT': DB_PORT,
    },
    'test': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': 'test_db.sqlite3',
    },
}

Here my .gitlab-ci.yml file

image: python:3.11.1

variables:
  DB_HOST: localhost
  DB_NAME: db_name
  DB_PORT: 5432
  DB_USERNAME: username
  DB_PASSWORD: password

stages:
  - Test

Test-job:
  
  stage: Test
  script:
  - pip install -r requirements.txt
  - cd core
  - python manage.py test

After running it, I receive the error below.

django.db.utils.OperationalError: could not connect to server: Connection refused
	Is the server running on host "localhost" (::1) and accepting
	TCP/IP connections on port 5432?
could not connect to server: Connection refused
	Is the server running on host "localhost" (127.0.0.1) and accepting
	TCP/IP connections on port 5432?

I understand that it cannot connect to the localhost because it’s on a seperate server, so I switched the default and test databases with each other. The job passed, but it lead to other complications with the databases. So I switched them back.

We plan on connecting to AWS RDS for the default DB later, but am being told that the job should pass before that. I spent all day yesterday looking for a solution, but I’ve got nothing.

Is there a way around this issue?

Is your local PostgreSQL DB on the same server as gitlab-runner you registered?