code: func isVowel(c rune) bool {
  	vowels := []rune{'a', 'e', 'i', 'o', 'u'}
  	for _, value := range vowels {
  		if value == unicode.ToLower(c) {
  			return true
  		}
  	}
  	return false
  }
docs: // isVowel returns true if the rune is a vowel (case insensitive).