concat.go

func concat(values []string) string {
    total := 0
    for i := 0; i < len(values); i++ {
        total += len(values[i])
    }

    sb := strings.Builder{}
    sb.Grow(total)
    for _, value := range values {
        _, _ = sb.WriteString(value)
    }
    return sb.String()
}