ci: migrate to Github Actions, close #546

[shinebayar-g]

Description

Let's migrate to Github Actions

Motivation and Context

See: #546 for more details

How Has This Been Tested?

I'm not Go developer, so I need your guidance to complete it. yml file syntax is pretty similar to travis ci. So I hope you'll be able to easily see what's going on.

Right now build is broken. Because of I don't know what's needed to fix. See builds here: https://github.com/shinebayar-g/oauth2-proxy/actions

Once we figure out travis ci replacement, we can move onto codeql action.

Checklist:

• My change requires a change to the documentation or CHANGELOG.
• I have updated the documentation/CHANGELOG accordingly.
• I have created a feature (non-master) branch for my PR.

[JoelSpeed]

golangci/golangci-lint info checking GitHub for tag 'v1.24.0'
golangci/golangci-lint info found version: 1.24.0 for v1.24.0/linux/amd64
install: cannot create regular file '/bin/golangci-lint': Permission denied
##[error]Process completed with exit code 1.

This is more of a bash problem at the moment. Looks like we need to install golangci-lint into some other directory, I wonder if we can do that easily using the existing go releaser scripts

On a separate note, if we do this migration, I'd like to keep travis and github actions on initially, so that we can compare the results and make sure there are no issues with the new CI. Can we drop the travis ci drop from this PR please?

I think it might be good to use this opportunity to create three status checks, one for linting, one for the tests and one for build, ie, does the code compile, this may require some changes to the Makefile targets but shouldn't be too much. I think we basically want to get the output of make lint, make build and make test but stop them depending on each other.

[JoelSpeed]

I think it might be good to use this opportunity to create three status checks, one for linting, one for the tests and one for build, ie, does the code compile, this may require some changes to the Makefile targets but shouldn't be too much. I think we basically want to get the output of make lint, make build and make test but stop them depending on each other.

@NickMeves @syscll @gargath WDYT of this suggestion?

[shinebayar-g]

@JoelSpeed I've figured most of the workflow. Now I'm not sure what to do with ./after build script.

[JoelSpeed]

Now I'm not sure what to do with ./after build script.

This needs to be in the test step, so I'd prefer if we had three separate jobs, which would give us three separate ticks right?

For the test one (make test), you need to have the before and after scripts in there too, so that it uploads the code coverage reports

[JoelSpeed]

Just gonna wait for checks to pass, then ready to merge!

Thanks @shinebayar-g