Go 读写锁

读写锁sync.RWMutext实现读者写者问题

package main

import (
    "fmt"
    "sync"
    "time"
)

var rwmutex *sync.RWMutex
var wg *sync.WaitGroup

func main() {
    rwmutex = new(sync.RWMutex)
    wg = new(sync.WaitGroup)

    wg.Add(4)
    go readData(1)
    go writeData(2)
    go readData(3)
    go writeData(4)

    wg.Wait()
    fmt.Println("main...over... ")
}

func writeData(i int) {
    defer wg.Done()

    fmt.Println(i, "准备写...")
    rwmutex.Lock()
    fmt.Println(i, "正在写...")
    time.Sleep(3 * time.Second)
    fmt.Println(i, "写结束(锁内)...")
    rwmutex.Unlock()
    fmt.Println(i, "写结束...")
}
func readData(i int) {
    defer wg.Done()

    fmt.Println(i, "准备读...")
    rwmutex.RLock()
    fmt.Println(i, "正在读取...")
    time.Sleep(3 * time.Second)
    fmt.Println(i, "读结束(锁内)...")
    rwmutex.RUnlock()
    fmt.Println(i, "读结束...")
}