Personally, I think that Rust's Option and Result are not well suited to Go. Option may serve a purpose, but the language was not built around these constructs. It's best (still IMO) to use generics to avoid code repetition, not to build semi-mathematical abstractions for their own sake right now. With time, we'll know how to use generics properly.

Without generics this is

    func (o IntToStringOption) Map(f func(a int) string) IntToStringOption { ... }
    // ... but that has to be repeated dozens of times

tbh I don't see it as much different. The func argument is the most complex part of the whole thing. And much of the readability comes from not using single-char type names, but you do learn to see past that with time.