Go: Length by Rune or Byte?

If I need to find the length of a string, I use built-in function len. At first I thought it returns the number of character, but actually it returns length of byte of the string.

	s := `something`
	println(len(s)) // return 9

this will print 9

but it will be different if I use utf8 chars

	s2 := "hétérogénéité"
	println(len(s2)) // return 18

this one return 18, because é is 2 bytes long and len is counting byte not char

so, if we want count chars in a string, we can use utf8.RuneCountInString

	s2 := "hétérogénéité"
	println(utf8.RuneCountInString(s2)) // return 13