package main

import (
    "fmt"
    "time"
)

var FormatISOTime = "2006-01-02T15:04:05.000Z07:00"
var FormatISOTimeoOmitted = "2006-01-02T15:04:05.999Z07:00"

func main() {
    t := time.Now()
    fmt.Println("====0填充")
    fmt.Println(t.Format(FormatISOTime))
    fmt.Println("====0忽略")
    fmt.Println(t.Format(FormatISOTimeoOmitted))
}

➜  t go run main.go
====0填充
2021-12-08T22:37:18.240+08:00
====0忽略
2021-12-08T22:37:18.24+08:00