golang官方指南给了一些代码片段来，层层递进演示了信道的能力:
1>. 信号量
2>. 限流能力
var sem = make(chan int, MaxOutstanding) func Serve(queue chan *Request) { for req := range queue { req:= req sem <- 1 go func() { // 只会开启MaxOutstanding个并发协程 process(req) <-sem }() } } 上面出现了两个信道：
① sem 提供了限制服务端并发处理请求的信号量
② queue 提供了一个客户端请求队列，起媒介/解耦的作用
进一步指南给出了信道的另一个用法：
3>. 解多路复用
多路复用是网络编程中一个耳熟能详的概念，nginx redis等高性能web、内存kv都用到了这个技术 。
这个解多路复用是怎么理解呢？
离散/独立/并发的客户端请求被服务端Serve收敛之后， Serve就起到了多路复用的概念，在Request定义resultChan信道，就给每个客户端请求提供了独立获取请求结果的能力，这便是一种解多路复用。
从实际效果看这就是常见的互联网web服务器：一款具备请求排队功能的并发限流服务器。
官方指南并没有完整实现客户端和服务器端工程。
下面是我的工程化实现， 记录下实践中遇到的问题。
并发受限服务器
信道queue接收客户端请求,解耦客户端和服务器，天然具备排队能力信号量信道sem提供了并发受限的能力- 服务器处理完，向
解多路复用信道req.resultChan写入响应结果。
/* 实现一个有请求队列功能的并发请求受限服务器*/ package main import ( "fmt" "sync" "time" ) var sem = make(chan int, Maxoutstanding) var wg2 sync.WaitGroup func server(queue chan *Request) { fmt.Printf("Server is already, listen req n") for req := range queue { req := req sem <- 1 wg2.Add(1) go func() { defer wg2.Done() process(req) <-sem }() } } func process(req *Request) { s := sum(req.args) req.resultChan <- s } func sum(a []int) (s int) { for i := 1; i <= a[0]; i++ { s += i } time.Sleep(time.Millisecond * 20) return s } time.Sleep模拟服务器处理请求单次耗时20ms， 输出数字的累加，
eg： input： 100；
output: 1+100/2*100 =5050
wg2 sync.WaitGroup是一个动态活跃的Goroutine计数器，注意用法和位置，wg2的作用是：等待所有请求处理完成。
并发客户端请求
for循环开启并发客户端请求，
- 每个请求入驻一个独立的Goroutine，独立向
信道queue投递请求和接收响应
package main import ( "fmt" "sync" ) type Request struct { args []int resultChan chan int } var wg1 sync.WaitGroup func clients() { fmt.Printf("start %d concurrency client requestn ", concurrencyClients) for i := 1; i <= concurrencyClients; i++ { r := &Request{ args: []int{i}, resultChan: make(chan int), } wg1.Add(1) go ClientReq(r) } wg1.Wait() } func ClientReq(r *Request) { defer wg1.Done() queue <- r go func() { res := <-r.resultChan fmt.Printf("current args is %d, the result is %d n", r.args[0], res) }() } wg1 WaitGroup的目的是确保所有的客户端请求都已经发出，之后客户端任务结束，所以此处我们新开Goroutine处理响应结果（这里又有闭包的参与）。
工程化
工程化代码的先后顺序，决定了代码是否死锁。
server需要处于监听状态，故先启动。
本处clients在主协程整体上是同步发送，如果放在
clients()的后面，clients内的wg1可能会有部分请求Goroutine阻塞在信道queue且没法唤醒 运行时会检测到报死锁。
package main import ( "fmt" "time" ) var concurrencyClients = 1000 var queueLength = 100 var queue = make(chan *Request, queueLength) // 请求队列长度 var Maxoutstanding int = 10 // 服务器并发受限10 func main() { go server(queue) var start = time.Now() clients() // 确保所有的请求都已经发出去 wg2.Wait() // 确保服务器处理完所有的请求 fmt.Printf("客户端并发%d请求，服务器请求队列长度%d，服务器限流%d，总共耗时%d ms n", concurrencyClients, queueLength, Maxoutstanding, time.Since(start).Milliseconds()) } 上面出现了3个配置变量
1>. 客户端并发请求数量concurrencyClients=100
2>. 服务器排队队列长度queueLength， 会作用到信道queue=50
3>. 服务器并发受限阈值Maxoutstanding=10
start 1000 concurrency client request Server is already, listen req current args is 14, the result is 105 current args is 2, the result is 3 current args is 3, the result is 6 current args is 1, the result is 1 current args is 4, the result is 10 current args is 8, the result is 36 current args is 6, the result is 21 current args is 12, the result is 78 current args is 5, the result is 15 current args is 7, the result is 28 current args is 18, the result is 171 current args is 16, the result is 136 current args is 15, the result is 120 current args is 20, the result is 210 current args is 19, the result is 190 current args is 13, the result is 91 current args is 21, the result is 231 current args is 10, the result is 55 current args is 17, the result is 153 current args is 9, the result is 45 current args is 22, the result is 253 current args is 28, the result is 406 current args is 27, the result is 378 current args is 11, the result is 66 current args is 26, the result is 351 current args is 30, the result is 465 current args is 23, the result is 276 current args is 25, the result is 325 current args is 29, the result is 435 current args is 24, the result is 300 current args is 31, the result is 496 current args is 34, the result is 595 current args is 38, the result is 741 current args is 36, the result is 666 current args is 41, the result is 861 current args is 32, the result is 528 current args is 35, the result is 630 current args is 33, the result is 561 current args is 37, the result is 703 current args is 39, the result is 780 current args is 52, the result is 1378 current args is 46, the result is 1081 current args is 47, the result is 1128 current args is 49, the result is 1225 current args is 45, the result is 1035 current args is 43, the result is 946 current args is 48, the result is 1176 current args is 40, the result is 820 current args is 42, the result is 903 current args is 44, the result is 990 current args is 59, the result is 1770 current args is 55, the result is 1540 current args is 53, the result is 1431 current args is 57, the result is 1653 current args is 51, the result is 1326 current args is 54, the result is 1485 current args is 50, the result is 1275 current args is 56, the result is 1596 current args is 58, the result is 1711 current args is 60, the result is 1830 current args is 66, the result is 2211 current args is 63, the result is 2016 current args is 70, the result is 2485 current args is 62, the result is 1953 current args is 61, the result is 1891 current args is 65, the result is 2145 current args is 67, the result is 2278 current args is 64, the result is 2080 current args is 68, the result is 2346 current args is 69, the result is 2415 current args is 76, the result is 2926 current args is 77, the result is 3003 current args is 71, the result is 2556 current args is 80, the result is 3240 current args is 75, the result is 2850 current args is 74, the result is 2775 current args is 73, the result is 2701 current args is 72, the result is 2628 current args is 78, the result is 3081 current args is 81, the result is 3321 current args is 89, the result is 4005 current args is 83, the result is 3486 current args is 88, the result is 3916 current args is 82, the result is 3403 current args is 79, the result is 3160 current args is 86, the result is 3741 current args is 84, the result is 3570 current args is 90, the result is 4095 current args is 85, the result is 3655 ...... current args is 981, the result is 481671 current args is 978, the result is 478731 current args is 982, the result is 482653 current args is 970, the result is 470935 current args is 979, the result is 479710 current args is 980, the result is 480690 current args is 983, the result is 483636 current args is 989, the result is 489555 current args is 986, the result is 486591 current args is 987, the result is 487578 current args is 985, the result is 485605 current args is 977, the result is 477753 current args is 988, the result is 488566 current args is 992, the result is 492528 current args is 976, the result is 476776 current args is 984, the result is 484620 current args is 995, the result is 495510 current args is 999, the result is 499500 current args is 1000, the result is 500500 current args is 990, the result is 490545 客户端并发1000请求，服务器请求队列长度100，服务器限流10，总共耗时2099 ms 读者可以随意调整3个参数的大小，来感受服务器调参的魅力。
| 并发客户端请求数concurrencyClients | 服务器请求队列queueLength | 服务器限流阈值 Maxoutstanding | 耗时ms |
|---|---|---|---|
| 1000 | 100 | 10 | 2067 |
| 1000 | 100 | 50 | 454 |
| 1000 | 100 | 100 | 210 |
| 1000 | 300 | 10 | 2082 |
| 1000 | 500 | 10 | 2071 |
| 3000 | 100 | 10 | 6259 |
| 5000 | 500 | 10 | 10516 |
That’s All,本文根据golang有关信道的指南， 实现了一个带有请求队列功能的首先服务器， 巩固了信道、WaitGroup的用法。
