Feature flags API in golang


Over the last few months, I’ve been interested in golang (the Go language) but I didn’t know what to build to really try it. Sure, I’ve done the exercises from the online tutorial and I’ve read the awesome website Go by example, but I didn’t have a real use-case yet. Until a few days ago when I decided to build an API related to feature flags!

What are feature flags?

Feature flags let you enable or disable some features of your application, for example when you’re under unexpected traffic or when you want to let some users try a new feature you’ve been working on. They decouple feature release and code deployment, so that you can release features whenever you want, instead of whenever the code happens to ship.

With this package, you can enable the access of a feature for:

  • specific user IDs
  • specific groups
  • a percentage of your user base
  • everyone
  • no one

And you can combine things! You can give access to a feature for users in the group dev or admin and for users 1337 and 42 if you want to.

What I’ve learned

I guess it’s a rather complete project because it involves a storage layer (a key-value store, with bolt), some logic around a simple model (what is a feature? How do we control access to a feature?) and an HTTP layer (with the default HTTP server and gorilla/mux). Moreover I’ve tried to write some tests, and it was really interesting to discover the “Go way” to do it!

Anyway, I’ve learned a lot and I’m fairly happy with the codebase, but if you spot anything that can be improved or that is wrong, please do get in touch with me (GitHub issues and tweets are perfect).

Here is the source code: github.com/AntoineAugusti/feature-flags.

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