that one has to goUsed to quote or report the idea that someone must go. It is formed from 가야 하다 (to have to go) plus the quotation marker 고, and is often followed by verbs such as 생각하다 (to think) or 말하다 (to say).
KO: 오늘은 병원에 가야 한다고 엄마가 말씀하셨어.
EN: Mom said that I have to go to the hospital today.