I was trying to speed up our slow CI by caching Go builds. The easy win was caching Go’s module downloads (via GOPATH), but when I added GOCACHE for the build cache, I got a pleasant surprise: the tests were caching too. 🥳

I shared the change for review, and a colleague raised a great point: “What about our black box integration tests?” These tests hit APIs and external services that Go can’t track as dependencies. If they cache when they shouldn’t, we might miss real failures: the tests would pass because they didn’t re-run, not because the code actually works.

I’m running an open source project called gocd-cli which is, well, a command line interface for Go continuous delivery. The intention is to make it easier to handle common tasks around Go. But this post isn’t really about that.

This project is supposed to be as portable as I can make it, becuse the original need I felt for it was born on RHEL6. Which is blessed with Python 2.6 by default. And we should definitely be looking to the future, meaning supporting Python 3, and I luckily got a pull request for just that. Since I couldn’t find any free hosted Go around I went for the next best thing, Snap CI, which is also built by ThoughtWorks.