Future With "Going to": Meaning

An action or decision that was made before the time of speaking (a plan).

I'm going to play football after work.

I play every week so this is a firm plan.

He's going to visit Thailand in August.

Look at those clouds! It's going to rain.

Future With "Going to": Form

Affirmative (Positive)

I am going to play football tonight

Form: Subject + am/is/are + going to + verb (infinitive)

 Negative

I am not going to play football tonight

Form: Subject + am/is/are + not + going to + verb (infinitive)

 Question (Interrogative) 

Are you going to play football tonight?

Form: Am/is/are + subject + going to + verb (infinitive)