Hi ,
I downloaded your logic and it seems correct. Do as Kilian suggests and encapsulate your logic on an server action that receives the coordinates as an input parameter and returns an address.
Since you're having issues, there (on the server action) you can add a breakpoint to see what's going wrong.
Also keep in mind what the API returns, since google always returns a list of composed addresses, you'll need to pick the one that suits your usecase.
Let me know if it worked or if you need an .oml with a sample.
Cheers,
Henrique