package main

import (
    "net"
    "time"
    "fmt"
)

func main() {
    // this is an "array" or "slice" (a collection of something)
    // the []string defines how it is to be stored, string is "text" where as an "int" or "integer" can only be a number
    // putting [] infront of a type (such as string or int) makes it a collection
    // in bash this is probably written something like Array("address1", "address2")
    hosts := []string{"10.0.0.200", "10.0.0.84", "google.com", "telstra.com", "syscad.net"}

    // this is a "for loop", it loops through a collection (array or slice)
    // in this example it will go through each item in hosts
    //             `range hosts`    // loop through hosts from start to end
    //     `host`                   // this is how you 'access' each item that's benig looped over
    // host will equal: "10.0.0.200" then "10.0.0.84" then "google.com" then "telstra.com" then "syscad.net" then stop
    for _, host := range hosts {

        // here I'm running a function, this is similar to running any command in bash with parameters
        // such as `ping 8.8.8.8` where 'ping'(checkIp) is the function name and '8.8.8.8'(host) is the parameter
        // I have an extra parameter here for port so you specifically target a service - 80 is for a web service,
        // but you could also target a printing port service
        checkIp(host, 80)
    }

}

func checkIp(host string, port int)  {

    // fmt.Sprintf is a text formatting package
    // here I'm setting `address` to address:port ie google.com:80
    address := fmt.Sprintf("%s:%d", host, port)

    // this is essentially the same as you netcat command
    // it attempts to connect to the address over tcp with a 5 second timeout (so it doesn't hang forever)
    conn, err := net.DialTimeout("tcp", address, time.Second * 5)

    // don't worry about this it's just cleaning up the connection as it will leave a network socket open if you don't
    if conn != nil {
        defer conn.Close()
    }

    // if there was an error with connecting (ie host is down) print out that the connection had failed
    if err != nil {
        fmt.Printf("%s failed\n", address)
    } else {
        // otherwise print out that it was a success
        fmt.Printf("%s success\n", address)
    }
}

// the output of this program is
//  10.0.0.200:80 success
//  10.0.0.84:80 failed
//  google.com:80 success
//  telstra.com:80 success
//  syscad.net:80 success