compare local to official us nist government time

time.go

package main

import (
	"encoding/xml"
	"fmt"
	"net/http"
	"os"
	"time"
)

func main() {
	start := time.Now()
	t, err := GovernmentTime()
	if err != nil {
		fmt.Fprintf(os.Stderr, "oops, error getting time: %v\n", err)
		os.Exit(1)
	}
	end := time.Now()
	rt := end.Sub(start) / 2
	mid := start.Add(rt)
	fmt.Printf("local (%s) - government (%s) = %v\n", iso(mid), iso(t), mid.Sub(t))
}

func GovernmentTime() (time.Time, error) {
	var t time.Time
	resp, err := http.Get("http://time.gov/actualtime.cgi")
	if err != nil {
		return t, err
	}
	defer resp.Body.Close()
	var x TimeXml
	d := xml.NewDecoder(resp.Body)
	if err := d.Decode(&x); err != nil {
		return t, err
	}
	t = time.Unix(0, 1000*x.Time)
	return t, nil
}

type TimeXml struct {
	Time int64 `xml:"time,attr"`
}

func iso(t time.Time) string {
	return t.Format("2006-01-02T15:04:05.000Z")
}