How to use "so here it goes?"

Question

How to use "so here it goes?".

I have written this sentence.

I have made up a short story. Here it goes.
When I was in ...

I am confused about what is the correct way to write it.

When should I use "here it goes" and "so here it goes"?

Which one of these is correct way to write and speak?

I have made up a short story. Here it goes.
I have made up a short story. So here it goes.
I have made up a short story, here it goes.
I have made up a short story, so here it goes.
I have made up a short story, here it goes:
I have made up a short story, so here it goes:

Answer 1

I think most native speakers wouldn't include a "subject" [pro]noun at all in OP's construction...

"I have made up a short story. [So] here goes."

That's because "Here goes" is an idiomatically standard expression equivalent to "Here I go", used as an exclamation calling attention to the fact that you're about to start doing something. It's often used in contexts where whatever you're doing is spectacular and/or risky.

Including the discourse marker so (or alternatives such as okay, right) is completely optional. But one function of such terms is to give the audience advance warning of a more significant utterance to follow. Since "Here goes" performs much the same role in OP's context, it's quite natural to use both methods (to make absolutely sure you have the full attention of your audience).

Answer 2

I've written a short story. [So] here [it] goes:

1. The expression here goes is a full sentence and thus, it's better for it to be in the form of a sentence.
2. Generally, Putting a full stop after goes or a colon instead doesn't really matter.
3. Had no idea if you figured it out or not, so here goes: So and it can get omitted from the expression.
4. Native people, unless they're really delicate grammarians, won't bother themselves with noticing the little error when using comma. (if any) A vast majority of clauses, or even sentences, in some circumstances, are fine to be separated by a comma, rather than a full stop. (Of course in case they don't trigger ambiguity or add up to confusion)
5. In short, the first suggestion of yours, with omitting "it", will be the optimum suggestion for most native speakers.