Calling PostgreSQL script from GitLab CI

.gitlab-ci.yml

# Credentials must be passed in through environment variables (DB_HOST, DB_PORT, DB_USER, DB_PASS, DB_NAME)
variables:
  DOCKER_DRIVER: overlay2
  GIT_STRATEGY: fetch
  PGPASSWORD: "$DB_PASS"

services:
  - docker:19.03.8-dind

stages:
  - example

job:
  stage: example
  image: alpine:3.12
  before_script:
    - apk add --no-cache postgresql-client
  script:
  - psql -U $DB_USER -h $DB_HOST -d $DB_NAME -p $DB_PORT -a -f script.sql