go - Does accessing elements of string as byte perform conversion?

Question

In Go, to access elements of a string, we can write:

str := "text"
for i, c := range str {
  // str[i] is of type byte
  // c is of type rune
}

When accessing str[i] does Go perform a conversion from rune to byte? I would guess the answer is yes, but I am not sure. If so, then, which one of the following methods are better performance-wise? Is one preferred over another (in terms of best practice, for example)?

str := "large text"
for i := range str {
  // use str[i]
}

or

str := "large text"
str2 := []byte(str)
for _, s := range str2 {
  // use s
}

Answer 1

Waitting for answers