[zer8k]

I didn't look too much at this but are they offering an alternative to the (IMO ugly) error checking pattern Go enforces? It's interesting to me shoehorning this into Go in particular. Go is notoriously stringent on how you write code.

[kadoban]

They have Either, so kind of. It looks serviceable, if a little messy without language support for safely destructuring its cases.

[bPspGiJT8Y]

Safe destructuring could be achieved with Church encoding.