main.go

package main

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

func main() {
	if len(os.Args) != 2 {
		fmt.Println("Please specify a host.")
		return
	}

	var host string = os.Args[1]
	var status bool = checkConnection(host)

	if status {
		fmt.Println(host + ": online")
	} else {
		fmt.Println(host + ": offline")
	}
}

func checkConnection(host string) bool {
	_, err := net.Dial("tcp", host)
	if err != nil {
		return false
	}

	return true
}