gopl-zh.github.com/vendor/gopl.io/ch5/trace/main.go

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2015-12-09 07:45:11 +00:00
// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 146.
// The trace program uses defer to add entry/exit diagnostics to a function.
package main
import (
"log"
"time"
)
//!+main
func bigSlowOperation() {
defer trace("bigSlowOperation")() // don't forget the extra parentheses
// ...lots of work...
time.Sleep(10 * time.Second) // simulate slow operation by sleeping
}
func trace(msg string) func() {
start := time.Now()
log.Printf("enter %s", msg)
return func() { log.Printf("exit %s (%s)", msg, time.Since(start)) }
}
//!-main
func main() {
bigSlowOperation()
}
/*
!+output
$ go build gopl.io/ch5/trace
$ ./trace
2015/11/18 09:53:26 enter bigSlowOperation
2015/11/18 09:53:36 exit bigSlowOperation (10.000589217s)
!-output
*/