code: func ScanUntil(data []byte, c byte) (n int) {
  	for {
  		i := bytes.IndexByte(data[n:], c)
  		if i == -1 {
  			return -1
  		}
  		n += i
  		if n == 0 || data[n-1] != '\\' {
  			break
  		}
  		n++
  	}
  	return
  }
docs: // ScanUntil scans for first non-escaped character c in given data.
  // It returns index of matched c and -1 if c is not found.