and the second value, of type <code>rune</code>, will be the value of
the corresponding code point.  If the iteration encounters an invalid
UTF-8 sequence, the second value will be <code>0xFFFD</code>,
the Unicode replacement character, and the next iteration will advance
a single byte in the string.
</li>

<li>
The iteration order over maps is not specified
and is not guaranteed to be the same from one iteration to the next.

}

// ToValidUTF8 treats s as UTF-8-encoded bytes and returns a copy with each run of bytes
// representing invalid UTF-8 replaced with the bytes in replacement, which may be empty.
func ToValidUTF8(s, replacement []byte) []byte {
	b := make([]byte, 0, len(s)+len(replacement))
	invalid := false // previous byte was from an invalid UTF-8 sequence
	for i := 0; i < len(s); {
		c := s[i]
		if c < utf8.RuneSelf {
			i++

and the second value, of type <code>rune</code>, will be the value of
the corresponding code point. If the iteration encounters an invalid
UTF-8 sequence, the second value will be <code>0xFFFD</code>,
the Unicode replacement character, and the next iteration will advance
a single byte in the string.
</li>

<li>
The iteration order over maps is not specified
and is not guaranteed to be the same from one iteration to the next.