map并发读写场景未加锁

package main

import "time"

func main() {
	m := make(map[int]int)
	go func() {
		for i := 0; i < 10000; i++ {
			m[0] = 1
		}
	}()
	go func() {
		for i := 0; i < 10000; i++ {
			_ = m[0]
		}
	}()

	time.Sleep(time.Second)
}

运行结果

go run加上race参数，输出存在data race的告警信息，只适用于运行时。

并发原语值拷贝

package main

import "sync"

func f(m sync.Mutex) {}

func main() {
	var m sync.Mutex
	f(m)
}