Every time I try to run swift code, I see some kind of error
How can I get rid of it?
It's not an error, it's a warning, so one simple option would be to live with it until it is proved to be harmful – then (and only then) you fix it.
Let's suppose this warning is bothering you and / or you have a zero warning policy and that's the only one preventing you doing so. I'd answer these questions in order to fix it:
After answering those questions (and provided that answering those didn't lead you to the target answer right away) I'd follow the favourite binary bisection technique to find the culprit that causes the warning – delete half of the app making sure the app still compiles and the warning is still in there, if the warning disappears - backtrack and delete the other half. Obviously if you made a change that causes other errors / warning you fix those first (typically by removing more code that depends on the just deleted parts). After you found the culprit and it is in the spotlight – at that point you'll probably have a good idea how to fix it.
Will give it a shot