Regarding GitLab CI — how have you worked with it, have you written yaml files yourself?

Yes, I have worked with GitLab CI and wrote .gitlab-ci.yml files for automation of builds and deployment.

In GitLab CI, a pipeline is described, consisting of stages, for example: build, test, deploy. Each stage specifies jobs with commands to execute.

An example of a simple .gitlab-ci.yml for a Go project:

stages:
  - build
  - test

build_job:
  stage: build
  image: golang:1.18
  script:
    - go build -o myapp
  artifacts:
    paths:
      - myapp

test_job:
  stage: test
  image: golang:1.18
  script:
    - go test ./...

I also configured dependency caching, artifacts, environment variables, and integration with Docker Registry.

GitLab CI allows flexible configuration of pipelines, triggering them by triggers, branches, and tags, which is convenient for CI/CD processes.