Test NTP offset from NIST

ntp_offset_test.go

package main

import (
        "fmt"
        "io"
        "log"
        "os"

        "github.com/beevik/ntp"
)

func main() {
        var (
                err  error
                nist *ntp.Response
        )
        for {
                nist, err = ntp.Query("time.nist.gov")
                if err != nil {
                        continue
                }
                break
        }

        targetList := []target{
                {7, "time%d.aliyun.com"},
                {4, "time%d.google.com"},
                {7, "time%d.apple.com"},
        }

        for _, t := range targetList {
                ali := make([]*ntp.Response, t.count)
                for i := 1; i < t.count; i++ {
                        ali[i-1], err = ntp.Query(fmt.Sprintf(t.formater, i))

                        if err != nil {
                                log.Print(err)
                                continue
                        }
                }

                for i, ao := range ali {
                        if ao == nil {
                                continue
                        }
                        io.WriteString(os.Stdout,
                                fmt.Sprintf("%s,%s\n", fmt.Sprintf(t.formater, i+1),
                                        (ao.ClockOffset - nist.ClockOffset).String()))
                }
        }
}

type target struct {
        count    int
        formater string
}