We come across will/going to in our day-to-day lives and they leave us confused about when to use either. Well, the difference is very subtle. Let’s discuss them:
We generally use will to talk about a future action. The action is only an intention. We use it to convey a decision that we made at the time of speaking i.e., a spontaneous decision. The decision is just made and expressed at the same time. It didn’t exist in the mind of the speaker before that moment.
Ex: I will call her tomorrow.
Here, the speaker just thought of calling someone tomorrow and expressed it right away. The thought didn’t exist in his/her mind before that moment.
Much like will, going to is used to talk about a future action. The action is still an intention. However, the difference lies in the time when the decision is made. Whereas will talks about a decision we made spontaneously, going to refers to a decision that was made long before it is expressed. Meaning, the decision was already on the mind of the speaker but he/she is only expressing it now. The decision wasn’t made at the time of speaking i.e., spontaneously.
Ex: I’m going to visit my relatives next week.
Note: Although they are both different, the difference between them is usually either ignored or non existent in spoken English. They can both be used interchangeably. So, there’s no need to worry about the accuracy of your sentence.