The Full Form of GGN is‍ Gotta Go Now.

It means you have to leave or ‘you have have to run’. This expression is often used when you are rushing to another appointment and you have to end the conversation.

It best used in the following context:

“I’ve got to go. I’ll call you later” or “I’ve got to go. We’ll talk later.”

It can be used in other contexts but the above way is the most commonly used way.

I have got to go= I gotta go —-it means ( I need to go = I should go or I have to leave now because of some important task that I need to officiate.

Some time we hear, “I gotta + noun “ . This means “ I got a + noun”. (I got a new car)

Have to, Have got to, Get to or Get are British Eng. grammar. Colloquially: gonna, wanna, gotta, “get, gets, got=is, are, were or was”