I've ranted about this before, but here we go again:

Go Plugins.

I was racking my brains trying to figure out how one could possibly implement plugins easily in Go.

I had a look at using RPC, which requires far to much boilerplate to be realistic. I looked at using Lua, but there doesn't seem to be a straight forward way of using it. I was even about to go with using WASM (yes, WASM). But then I came across Yaegi ("Yet another elegant Go interpreter", you heard right: "interpreter"), Yaegi is also very easy to use.

There are a few issues (including some I haven't solved yet), including flexibility (multiple types of plugins), module support, etc. Fortunately, Traefik just released their plugin system which is based on Yaegi (same company), and I got to learn a few tricks from them.

Here's how module loading works: The developer vendors their dependencies and pushes them to a repo. The user downloads the repo as a zip and saves it to the plugins folder. I hash the zip, unzip it to a cache, and set the the GOPATH for the interpreter to be that extracted folder. I then load the module (which is defined by a config file in the folder), and save it for later. This is the relatively easy part.

The hard part is allowing for different types of plugins. It looks easy, but Go has a strict typing system, makes things complicated. I'm in the process of solving this problem, and so far it should go like this: Check that the plugin fits an arbitrary interface, and if it does, we're good the go. I will just have to apply the returned plugin to that interface. I don't like this method for a few reasons, but hopefully with generics it will become a bit more clean.