Monitor web page changes with Go, forked and minified from https://gist.github.com/ssimunic/47834a8fcc3d66d6d7502e916f7ef613

main.go

package main

import (
    "net/http"
    "io/ioutil"
    "time"
    "log"
    "os"
)

const LoopEverySeconds = 5
var client = &http.Client{}
var url string
var lastData string

func checkChanges(newData string) {
    if newData == lastData {
        log.Println("No changes.")
        return
    }
    log.Println("Changes noticed!")
    os.Exit(0)
}

func makeRequest() {
    req, err := http.NewRequest("GET", url, nil)
    resp, err := client.Do(req)
    data, err := ioutil.ReadAll(resp.Body)
    if lastData == "" {
        lastData = string(data)
    } else {
        checkChanges(string(data))
        lastData = string(data)
    }
}

func scheduleRequests() {
    for range time.Tick(time.Second * LoopEverySeconds) {
        makeRequest()
    }
}

func main() {
    url = os.Args[1]
    makeRequest()
    scheduleRequests()
}