친구 따라 강남 간다고 · 친구 따라 강남 가다
to do something just because a friend does it (lit. to follow a friend all the way to Gangnam)
Example
친구 따라 강남 간다고, 친구가 등록해서 저도 요가를 배우게 됐어요.
I just followed my friend's lead: she signed up, so I ended up learning yoga too.
Word parts
친 intimate+구 old+강 river+남 south
This 강남 is not Seoul's Gangnam district but the old 'land south of the river' (the Yangtze in China), a warm faraway place where swallows were said to fly for the winter.
Good to know
Used lightly about joining something only because a friend did, whether out of peer pressure or by happy accident.