We should save Go from the current crisis of overconfident narcissistic idiocy.
In the good old times only very few people, who have passed through harsh selection (basically, you have to me Math or EE major) were allowed into PL design. Out of that we got APL, Smalltalk, Common Lisp, Scheme, Miranda, Haskell, Standard ML and Scala - all the nice things.
When demagogues and narcissistic bullshitters were allowed to design a language we got C++, Java with all the inconsistencies and sloppy kitchen sink thinking which are so characteristic of Liberal Arts majors.
So, Go has been famous for keeping the list of features small, orthogonal (on the implementation side) and complementary (on the semantic side). It is precisely this what makes it such a success.
It has a multiple return values (not a tuple) similar to Common Lisp and this is the best we could have. Literally.
Introducing the full-blown type-classes (or better to call them type-traits, suggesting that they are composable, or flavors as they used to be named by Symbolics) is a too much effort, basically a design from scratch is required.
Just adding a Maybe monad, as idiots are suggesting, is a bullshit "solution" since it requires type-classes in the first place.
If you are that fucking smart (hint: you are not - thousands of exponentially brighter people have pushed the field since 60s especially in Common Lisp and ML communities) - just fork the language and make it your way, but, please, leave us alone and stop spamming us with your naive bullshit.