code: func (db *Database) replaceMarks(in string) string {
  	var buffer bytes.Buffer
  	for _, runeValue := range in {
  		if runeValue == '?' {
  			buffer.WriteString("$")
  			buffer.WriteString(strconv.Itoa(db.varCount))
  			db.varCount++
  		} else {
  			buffer.WriteRune(runeValue)
  		}
  	}
  	return buffer.String()
  }
docs: // replaceMarks replace question marks (?) with the PostgreSQL variable identifier
  // using the right (incremental) value