sync.once 确保执行一次 sync.map并发安全版map finished

sync/sync.map.go

@@ -0,0 +1,32 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"sync"
+)
+
+// GO内置的map不是并发安全的
+var m = make(map[string]int)
+
+func get(key string) int {
+	return m[key]
+}
+
+func set(key string, value int) {
+	m[key] = value
+}
+
+func main() {
+	wg := sync.WaitGroup{}
+	for i := 0; i < 10; i++ {
+		wg.Add(1)
+		go func(n int) {
+			key := strconv.Itoa(n)
+			set(key, n)
+			fmt.Printf("k=:%v,v:=%v\n", key, get(key))
+			wg.Done()
+		}(i)
+	}
+	wg.Wait()
+}

sync/sync.map_example.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"sync"
+)
+
+// 并发安全版map
+//无需初始化
+var sm sync.Map
+
+func main() {
+	w := sync.WaitGroup{}
+	for i := 0; i < 10; i++ {
+		w.Add(1)
+		go func(n int) {
+			defer w.Done()
+			key := strconv.Itoa(n)
+			sm.Store(key, n)         //必须使用sync.Map内置的store方法去设置键值对
+			value, _ := sm.Load(key) //必须使用sync.Map内置的load方法取值
+			fmt.Printf("k:%v,v:%v\n", key, value)
+		}(i)
+	}
+	w.Wait()
+}

sync/sync.once.go

@@ -0,0 +1,42 @@
+package main
+
+import "sync"
+
+//某些操作只需要在高并发场景中做一次，例如加载配置文件
+//这种场景下用到sync.once
+
+var waitGroup sync.WaitGroup
+var once sync.Once
+
+func send(ch1 chan<- int) {
+	defer waitGroup.Done()
+	for i := 0; i < 100; i++ {
+		ch1 <- i
+	}
+	close(ch1)
+}
+func getV(ch1 <-chan int, ch2 chan<- int) {
+	defer waitGroup.Done()
+	for {
+		x, ok := <-ch1
+		if !ok {
+			break
+		}
+		ch2 <- x * x
+	}
+	once.Do(func() { close(ch2) })
+}
+
+func main() {
+	a := make(chan int, 100)
+	b := make(chan int, 100)
+	waitGroup.Add(3)
+	go send(a)
+	go getV(a, b)
+	go getV(a, b)
+	waitGroup.Wait()
+	for ret := range b {
+		println(ret)
+	}
+
+}