Be going to: form
We use be going to + the base form of the verb:
I’m going to take a few exams at the end of the year.
It’s going to be difficult to get a job during the summer as the tourist industry is suffering from the economic downturn.
Be going to: uses
Be going to is commonly used in informal styles.
Intentions
We use be going to to talk about future plans and intentions. Usually the decision about the future plans has already been made:
She’s going to be a professional dancer when she grows up.
I’m going to look for a new place to live next month.
Predictions
We use be going to to predict something that we think is certain to happen or which we have evidence for now:
It’s going to snow again soon. (The speaker can probably see dark snow clouds.)
Look out! He’s going to break that glass.
Commands
We use be going to when we give commands or state that something is obligatory:
[parent to a child]
You’re going to pick up all of those toys right now. This room is a mess!
Gonna (informal contexts)
Spoken English:
We use gonna /gənə/ instead of going to in informal contexts, especially in speaking and in song lyrics. We write gonna to show how to pronounce it:
Are you gonna try and get stuff sorted as soon as you can then? (Are you going to try and get things organised as soon as you can?)
One day I’m gonna be a star.
Be going to or will?
Will is often used similarly to be going to. Will is used when we are talking about something with absolute certainty. Be going to is used when we want to emphasise our decision or the evidence in the present:
[An ‘A’ road is a main road. A ‘B’ road is a smaller road.]
We are now very late so we’re going to take the ‘B’ road. (the speaker refers to the present and emphasises the decision)
I know the ‘B’ road will be quicker at this time of day. (the speaker states a fact).
https://dictionary.cambridge.org/pt/gramatica/gramatica-britanica/future/future-be-going-to-i-am-going-to-work
