[eyelidlessness]

I upvoted both your comment and GP. Here, hopefully this helps your comment feel more productive: this is a Result type, albeit yes not a Monad. It’s (AFAIK) the idiomatic way the type is expressed in Go, so maybe cumbersome to implement but trivial to adopt.

It’s also something I realized was lost in the JS progression towards Promise APIs and eventually async/await. Promises have ergonomic benefits over callback hell, but damn if the Node convention of cb: (error, result) => { /* … */ } wasn’t a Result type sitting there begging to be embraced. Again, not a Monad, but it’s a shame the good API design was thrown out with the inconvenient API design.