You can’t. You can only pass generic functions which can have several methods. However, the call goo(a, 10) will pick the appropriate method of goo (or error if there is none). So you should be ok.
Jeff’s thesis is a good read: phdthesis/main.pdf at master · JeffBezanson/phdthesis · GitHub.
PS: check out PSA: how to quote code with backticks and welcome!