while at it, since you're already doing it, on the occasion
This expression is used when an action or state of affairs resulting from the action in the preceding clause becomes an opportunity to also do another originally unplanned but related action in the following clause.
1. Even if the action expressed in the preceding clause happened in the past, this expression can be used in the present tense form -는 김에 as long as the action described in the following clause happened almost at the same time as the preceding action.
2. Even when expressing something occurring in the present, if the action in the preceding clause is completed before the action in the following clause begins, then the form -(으)ㄴ 김에 is used.
While the expressions -(으)ㄹ 겸 -(으)ㄹ 겸 and -는 김에 are similar with respect to the fact that they indicate combining or doing together of two actions, they have the following differences.
Expresses doing another action while doing something else, taking advantage of the situation.