mirror of
https://github.com/gopl-zh/gopl-zh.github.com.git
synced 2024-11-14 02:13:51 +00:00
41 lines
831 B
Go
41 lines
831 B
Go
// 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
|
|
*/
|