I'm glad to see this idea getting some traction again. I haven't used Go much in the last few years, but I started playing around with a similar idea back in 2016 when I was working on a small compiler for a configuration management tool, and later put together a small stand-alone proof of concept library(https://github.com/rebeccaskinner/gofpher) as part of a talk (https://speakerdeck.com/rebeccaskinner/monadic-error-handlin...) I gave in 2017.

At the time, I remember finding FP in go surprisingly ergonomic. Implementing the library to support it was a pain since the type system wasn't expressive enough to prevent everything from devolving into a pile of untyped reflection, but it was reasonably easy to keep that an implementation detail. On the whole, I felt like go would have lent itself well to the "dash of FP for flavor" style of programming that seems to be gaining popularity these days. Unfortunately, in 2017 at least, the Go community seemed to have very little interest in the idea.

I still have a fondness for Go. It always felt nice to use. If the language features have caught up to the point where a robust library like this is feasible, and the communities attitude has shifted, I might take another look at the language.