I know we can use 'will be' to talk about future facts, eg.
l will be 34 tomorrow.
But, can we use 'going to be' instead of 'will be', at least in informal situations?
l'm going to be 34 tomorrow.
Although will and going to are different in some ways, in casual speech and writing, will and going to are often interchanged.
When we want to talk about future facts or things we believe to be true about the future, we use will.
going to be
construction is informal,will
can be used in both formal and informal situations.