performance - How expensive is []byte(string)?

Question

Let's convert string to []byte:

func toBytes(s string) []byte {
  return []byte(s) // What happens here?
}

How expensive is this cast operation? Is copying performed? As far as I see in Go specification: Strings behave like slices of bytes but are immutable, this should involve at least copying to be sure subsequent slice operations will not modify our string s. What happens with reverse conversation? Does []byte <-> string conversation involve encoding/decoding, like utf8 <-> runes?

Answer 1

Waitting for answers