Forgejo Actions and version numbers

Let me be on the record that I hate working on a CI pipeline. It brings me back to a time when we made a single line change and waited ten minutes for C++ templates to compile. I really did not enjoy that. This will serve as documentation so I never have to figure this out again. I have a Go app for which I want to build a Docker image for the app. The build is dispatched manually via the web ui of Forgejo. I want to specify the version number of the build when dispatching the job. Let us get into it.

First we need a variable somewhere in our Go app to inject the version number as build time flag.

// cmd/app/main.go
var Version string

Next we update the Docker file to accept an argument and add the flag to our Go build command.

ARG APP_VERSION
RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags "-X 'main.Version=${APP_VERSION}'" -o /app cmd/app/main.go

Last but not least: Time to update Forgejos workflow. I am using buildx and build-push-action to build the Docker image. Here are the relevant parts. We update the workflow_dispatch section to accept an input.

on:
  workflow_dispatch:
    inputs:
      version:
        description: "Version"
        required: true
        type: string

now with the variable version holding our input, we can add it as a build argument to the build-push-action.

- name: Build and Push
              uses: https://github.com/docker/build-push-action@v4
              with:
                  pull: true
                  push: true
                  tags: ${{ github.repository }}:${{ inputs.version }}
                  platforms: linux/amd64
                  file: Dockerfile
                  context: .
                  build-args: |
                    APP_VERSION=${{ inputs.version }}

Nicely tagged Docker images and the app, once compiled, also knows which version it is supposed to be. Great success.