Be going to

1. We use it to talk about predictions for the future that are based on present evidence. 

• Look at the black clouds! It’s going to rain.
• He’s driving too fast. He’s going to crash.

2. We use the structure be going to when we speak about our plans, intentions, or ambitions for the future; we have already decided to do something. 

• I’m going to buy some new shoes at the weekend.
• We’re going to get married soon.