Nice. I prefer my solution because it's clear what's going on.

Thanks. I admit that in the course of my day-to-day I don't leave such detailed comments but here I figured maybe someone could benefit from them.

There is an issue on the attempt in Go. It's failing when nbBear is 9 and yet the length of the whole pair output is 10, meaning only 5 pairs. Therefore, should be false, not enough but it's failing the attempt saying it should be true.

Nice but the initial ToLower is a full iteration that's not necessary as you can just convert each rune to lowercase in your first for loop

Super clever but I don't consider this best practice since if you change any part of the problem this solution becomes useless. For example, if multiple numbers could have odd counts or you were asked for a specific count like 2, 5, 7, etc. Super clever though.