This is a template for a GitHub Action written in Go 1.12. I put it together after building my Labeler action (which you can use as a real-life example). Below is a brief explanation of all the pieces so you can start your own action from there. There will be inacuracies and mistakes (I have inferred much of this info from existing actions, and the GitHub docs are still under development). Feel free to throw an Issue or PR at me with corrections.

This is your application code. In our template we simply output "Hello World!" to the Action's execution log. Just change this code.

The main purpose of this file is to define the container that your code will run in.

You don't need to publish the container to a Docker registry: GitHub is able to execute your action by giving it a reference to your repo (such as srvaroa/github-action-go-template@master). However, if you chose this option the container will be built in every single execution of the action (in other words, it'll be slower to execute.)

If you're wondering about which icons are available, you can chose any from feathericons.com

This file defines metadata for the action. Some of it seems redundant with the Dockerfile so I suspect some of this may dissappear after the Beta period. The documentation I could find for this file is at Actions toolkit

I'll skip the bits that are self-explanatory. Two sections are more interesting:

runs: using: 'docker' image: 'Dockerfile' 

GitHub actions supports two types of actions NodeJs or Docker containers. In our case we need a container so we set 'docker'.

The image property lets us tell GitHub how to get the executable version of our action. In our case, we're setting Dockerfile to specify we want it to use the [#Dockerfile] in our repo. If you prefer to publish an image to a registry, then you should change this value to the image reference.

inputs: my_property: description: "My custom input property" default: "some_default_value" 

This defines a configuration option my_property with a description and a default value. This property is made available to your application as an environment variable INPUT_MY_PROPERTY that is injected in your container by the GitHub Actions runtime.

These properties are useful if you want to give users of your action the ability to pass configuration to the action. The owner of the repo would add a with property to the uses section:

 - uses: srvaroa/github-actions-go-template@master with: my_property: some_other_value 

A real example of an action that uses this feature extensively is the Checkout action. I'll show how to use it below.

To execute the action from any other repository, you only need to create a workflow definition file like .github/workflows/main.yml.

name: Say Hello on: [push] jobs: build: runs-on: ubuntu-latest steps: - uses: srvaroa/github-actions-go-template@master 

This will execute the action srvaroa/github-actions-go-template, from the master branch, on every push to the repo.

Here are a couple of screenshots of how it working, commits in the master branch now get a check if the action passes.

<img src="images/commits.jpg" /> 

If you click on details, you see the full log.

<img src="images/action.png" /> 

After writing your own action, just change the uses section as appropriate and you're set. You probably want to use a SHA or a tag instead of master.

To override the default for my_property that we declared in the inputs section, the workflow file would look like this.

name: Say Hello on: [push] jobs: build: runs-on: ubuntu-latest steps: - uses: srvaroa/github-actions-go-template@master with: my_property: some_other_value 

Check the official documentation for workflows if you want more info on using actions.

You can build and run your container locally with:

$ docker build -t github-actions-go-template . $ docker run -it github-actions-go-template 2019/08/27 15:49:14 Hello world! 

The old documentation is at https://developer.github.com/actions/creating-github-actions/, but it will be removed on Sept 30th 2019 according to the deprecation notice.

The new documentation is at https://help.github.com/en/categories/automating-your-workflow-with-github-actions