docs: channel 生产者/消费者

base/channel/example/main.go

@@ -3,13 +3,12 @@ package main
 import (
 	"fmt"
 	"sync"
+	"sync/atomic"
 )
 
 var wg = new(sync.WaitGroup)
-var once = new(sync.Once)
 
-//consumerNum := int32
-//var consumer = atomic.N
+var consumer = int32(0)
 
 func f1(ch chan int) {
 	defer wg.Done()
@@ -27,17 +26,22 @@ func f2(in chan int, out chan int) {
 		out <- i * i
 	}
 
-	once.Do(func() {
+	if atomic.AddInt32(&consumer, -1) <= 0 {
 		// 使用完必须 close 不然将导致死锁
 		close(out)
-	})
+	}
 }
 
 func main() {
 	ch := make(chan int, 20)
 	ch2 := make(chan int, 5)
-	wg.Add(2)
+
+	wg.Add(1)
 	go f1(ch)
+
+	wg.Add(2)
+	atomic.AddInt32(&consumer, 2)
+	go f2(ch, ch2)
 	go f2(ch, ch2)
 
 	for i := range ch2 {