In your new hotness, I believe that handler is already implicit, so you can just leave it off.

What I am still curious about, and can't see whether or not is possible from the current draft (possible I've just skimmed too hard) is whether printSum can become:

    func printSum(a, b string) error {
        fmt.Println("result:",
            check strconv.Atoi(a) +
            check strconv.Atoi(b))
        return nil
    }

Possibly with an addition paren around the check.

(I'm just using this as an example; in this case I probably would assign x & y on separate lines since in this case this saves no lines, but there are other cases where I've wanted to be able to call a function that has an error but avoid the 4-line dance to unpack it.)