The Go decision was explicitly to not have warnings, and the unused identifier thing complained about is merely a consequence of that.
Q. Why can’t I have feature X?
A. We thought of that already, and your opinion is wrong.
Q. But basically every other language in existence supports this. And it makes development easier. We would really, really like it. Please?
A. Apparently you don’t get it. Here’s a pointer to a 15 year-old post on a mailing list where the first time someone asked for this, we said no. Your opinion is wrong.
Sounds like we agree!