检查字符是否为俄语

I would like to know if a string contains Russian/Cyrillic characters.

For latin characters, I do something like this (pseudocode):

text := "test"
for _, r := range []rune(text) {
    if r >= 'a' && r <= 'z' {
        return True
    }
}
return False

What is the corresponding way to do it for Russian/Cyrillic alphabet?

This seems to work

unicode.Is(unicode.Cyrillic, r) // r is a rune

I went on and did this example implementation for finding russian uppercase chars, based on this Unicode chart:

func isRussianUpper(text string) bool {
    for _, r := range []rune(text) {
        if r < '\u0410' || r > '\u042F' {
            return false
        }
    }
    return true
}

You can do any set of characters this way. Just modify the codes of characters you are interested in.