I usually hear 路 used with 條 as the classifier, but sometimes people also use 個. in cantonese, which is the correct classifier? are both correct?
"條" is the correct one. I speak Cantonese and never heard of "個" in this case.
In some cases, people who are bilingual in Mandarin and Cantonese might use 個 and 條 as classifier interchangeably for road (路). In Chinese, 個 is a universal classifier or measure word for objects, you might hear it in many occasions to count a "stuff" even for a native speaker.
條(tiu4) is the proper classifier for 路(lou6). You have been hearing 個(go3) might because the person was referring to 路(lou6) 口(hau2), which means the corner of the street.