There are no flags in yes(1) ergo there's no need for "flag parsing". yes(1) takes one optional string as input, and that's exactly what argv provides. I'm not sure what you think "flag parsing" is bringing to the table here, but checking the array of command line parameters and accessing an element is pretty far from a hack.
If it's more comfortable you can also declare argv as an array of character arrays e.g. char *[], but that won't change the line count.
But you're also arguing in bad faith. Your go code is shorter, okay, but it doesn't do the same thing as the GNU yes code, so what point are you trying to make? I can also link to philosophy 101 wikipedia articles:
I think I have made it pretty clear already, but here it is again:
the Go code has MORE functionality (flag parsing) with LESS code. yes its not as fast, and yes the executable is larger, but for many, thats a good tradeoff for the extra standard library features, and the reduced LOC/code complexity. sadly as of yet, I haven't seen any cogent technical arguments against my points thus far.
If it's more comfortable you can also declare argv as an array of character arrays e.g. char *[], but that won't change the line count.