There are sooooooooooo many verb endings in Korean but I'll list you the most important ones.
가다 dictionary form
가(요) simple present (formal 갑니다)
가고 있어(요) present continuous (formal 가고 있습니다)
갔어(요) simple past (formal 갔습니다)
갈 거야 (거예요) simple future (formal 갈 겁니다)
갈게(요) when proposing your help to someone, or to soften what you're saying to not sound rude
가겠어(요) uncertain future, or expresses determination/volition
가자 let's go (formal 갑시다)
가면 if I go
가지(요) expresses that your listener knows what you're talking about
가잖아(요) when correcting someone
가는데 but, or as a connective verb ending before asking a question
가지만 but
가기 -ing (not always usable, there are some set expressions -기를 바라다/원하다, -기 전에, -기 위해)
가서 indicating a reason (cannot be used if result is imperative)
가니까 indicating a reason (can be used if result is imperative)
갈 수 있어(요) can go
갈 수 없어(요) can't go
못 가(요) / 가지 못해(요) can't go
안 가(요) / 가지 않아(요) doesn't go
가야 해(요)/돼(요) I have to go
가니 interrogative, can sound feminine
가냐 interrogative, can sound mischievous
갈까(요) interrogative, wondering something, talking to yourself
가나(요) interrogative (without the -요 it's the same as 갈까, with the -요 you can add it to any question)
갑니까 formal interrogative
간 past adjective (간 곳 the place I went to)
가는 present adjective (가는 곳 the place I go/am going to)
갈 future adjective (갈 곳 the place I will go to)