Meaning the same thing as the last "g" is added.
To make yourself sound "in". Also to make yourself sound stupid and pretentious if you precisely pronounce it as "goi-N", unless you are trying to be funny.
Eclectically and neutrally, some Americans prefer a pronunciation between "going" and "goin", not belonging to either one, strictly. To make themselves sound kinda cowboy, lazy, Americanistic, uninterested, indifferent, vital, young, in, etc.