Golang : Convert file unix timestamp to UTC time example

This tutorial is my own notes from helping out a friend from my working days in Indonesia. Putting it here in case it maybe useful to you.

• He wanted to use Go to process JSON data output from an old/orphaned server.
• The person in charge of the server left the company long time ago and the JSON output can't be modified at the mean time until someone take ownership of the orphaned server.
• The backup file names are differentiated by milliseconds and the JSON output will only give Unix time stamp.

NOTE : the unix time stamps are used for naming the backup directories.

A file information query to the remote server will return the following JSON encoded data:

 { 
 "filename" : "backupCDRfiles.raw", 
 "lastModified" : 1439167001616
 }

the lastModified field is in unix timestamp format and he needs to convert unix timestamp into UTC format for readability purpose.

The code sample below will convert the file unix timestamp to millisecond format.

 package main

 import (
  "encoding/json"
  "fmt"
  "time"
 )

 type FileInfo struct {
  FileName string `json:"filename"`
  MilliSecond int64  `json:"lastModified"`
 }

 func (f FileInfo) PrintFileName() string {
  return string(f.FileName)
 }

 // method to convert file unix timestamp to UTC
 // need to convert f.MilliSecond to nano seconf first for time.Unix() function to work
 // see http://golang.org/pkg/time/#Unix

 func (f FileInfo) PrintTime() time.Time {
  return time.Unix(0, f.MilliSecond*int64(time.Millisecond))
 }

 var JSONstr = `{ 
 "filename" : "backupCDRfiles.raw", 
 "lastModified" : 1439167001616
 }`

 func main() {

  var fInfo FileInfo

  err := json.Unmarshal([]byte(JSONstr), &fInfo)

  if err != nil {
 panic(err)
  }

  fmt.Println(fInfo)

  fmt.Println("File name is : ", fInfo.PrintFileName())
  fmt.Println("File last modified time in millisecond : ", fInfo.PrintTime())
 }

Output :

{backupCDRfiles.raw 1439167001616}

File name is : backupCDRfiles.raw

File last modified time in millisecond : 2015-08-10 00:36:41.616 +0000 UTC

Play at : https://play.golang.org/p/7fwdmp_0nO

Reference :

http://golang.org/pkg/time/#Unix