code: func ReadString(r *bufio.Reader) Value {
  	ReadWhitespace(r)
  	if !ReadStringStart(r) {
  		return nil
  	}
  	result := ReadDataUntil(r, untilFixed('"'))
  	if !ReadStringEnd(r) {
  		return nil
  	}
  	return Sstring(result)
  }
docs: // ReadString will read a string from the reader