This is the 8853rd most frequent Korean word.
갔다고
"갔다고" means "said [someone] went" or "claimed [someone] went" in English.
The word '갔다고' is used to relay what was said, specifically to indicate that the person stated their action of going to school.
그는 학교에 갔다고 말했어요.
He said that he went to school.
Here, '갔다고' is used to express hearsay or reported information about the action of going to the park.
친구들이 공원에 갔다고 들었어요.
I heard that friends went to the park.
In this sentence, '갔다고' is used to indicate a future claim in reported speech about attending a party.