Function elapsed time in golang from http://play.golang.org/p/U58I5eGXRY

elapsed.go

package main

import (
	"log"
	"time"
)

func whenDone() func(format string, args ...interface{}) {
	start := time.Now()
	return func(format string, args ...interface{}) {
		log.Printf(format, append(args, time.Since(start))...)
	}
}

func process(name string) {
	defer whenDone()("total time processing %v: %v", name)
	
	log.Printf("started processing %v", name)
	time.Sleep(time.Second)
}

func main() {
	process("foo")
}