[fixermark]

IIUC, the go-idiomatic way to do this if you find yourself wanting default arguments is to pass in a struct as one of the args to your function and have the default values of the fields in the struct mean "default" in the behavior of the function.

But in general, if you have a two-argument function and one of the arguments could be defaulted, just pass it. It's clearer at the call point what's happening then.