sync.mutex是结构体，值传递

错误代码，结构体是值传递，将mutex传进去，体现不了效果。

package main

import (
   "fmt"
   "math/rand"
   "sync"
   "time"
)

var count int

var mutex sync.RWMutex

func write(n int, mutex sync.RWMutex) {
   time.Sleep(2 * time.Second)
   rand.Seed(time.Now().UnixNano())
   fmt.Printf("读 goroutine %d 准备写锁...\n", n)
   mutex.Lock()
   fmt.Printf("写 goroutine %d 正在写数据...\n", n)
   time.Sleep(5*time.Second)
   num := rand.Intn(500)
   count = num
   fmt.Printf("写 goroutine %d 写数据结束，写入新值 %d\n", n, num)
   time.Sleep(3 * time.Second)
   mutex.Unlock()

}
func read(n int, mutex sync.RWMutex) {

   fmt.Printf("读 goroutine %d 准备读锁...\n", n)
   mutex.RLock()
   fmt.Printf("读 goroutine %d 正在读取数据...\n", n)
   time.Sleep(20 * time.Second)
   num := count
   fmt.Printf("读 goroutine %d 读取数据结束，读到 %d\n", n, num)
   mutex.RUnlock()
   time.Sleep(5 * time.Second)
}
func main() {
   var mutex sync.RWMutex
   for i := 0; i < 1; i++ {
       go read(i + 1, mutex)
   }
   for i := 0; i < 1; i++ {
       go write(i + 1, mutex)
   }
   time.Sleep(time.Second * 35)
}