You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: main.go
    path of file: ./repos/goHackTools/projects/31_lookupIP
    
    the code of the file until where you have to start completion: package main

import (
	"fmt"
	"log"
	"net"
	"os"
)

func main() {
	// usage
	if len(os.Args) == 1 || os.Args[1] == "-h" {
		usage(os.Args[0])
	}

	arg := os.Args[1]

	// Parse the IP for validation
	ip := net.ParseIP(arg)
	if ip == nil {
		log.Fatal(
    
func main() {
	// usage
	if len(os.Args) == 1 || os.Args[1] == "-h" {
		usage(os.Args[0])
	}

	arg := os.Args[1]

	// Parse the IP for validation
	ip := net.ParseIP(arg)
	if ip == nil {
		log.Fatal("Valid IP not detected. Value provided: " + arg)
	}

	fmt.Print(arg + "\t")

	hostnames, err := net.LookupAddr(ip.String())
	if err != nil {
		log.Fatal(err)
	}

	for i := range hostnames {
		fmt.Print(hostnames[i])
	}
}