golang sync.Mutex

//go func 和主线程之间的关系是并行和竞争关系

package main

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

var l sync.Mutex
var m *sync.Mutex

func main() {

    m = new(sync.Mutex)

    go lock(1)
    time.Sleep(3 * time.Second)

    fmt.Printf("%s\n", "exit!")

}
func lock(i int) {
    println(i, "lock start")

    m.Lock()
    println(i, "lock")

    time.Sleep(3 * time.Second)

    m.Unlock()
    println(i, "unlock")
}