1. Golang協程

• golang和其它語言最大區別莫過于goroutine，也就是go的協程，example如下：

package mainimport "fmt" import "time"func go_worker(name string) {for i:=0; i<10; i++ {fmt.Println("this is go worker :" , name)} }func main(){go go_worker("lineshen")go go_worker("glorialu")time.Sleep(time.Second*5) // print effectivefmt.Println("main finished") }

輸出：

this is go worker : lineshen this is go worker : lineshen this is go worker : lineshen this is go worker : lineshen this is go worker : lineshen this is go worker : lineshen this is go worker : lineshen this is go worker : lineshen this is go worker : lineshen this is go worker : lineshen this is go worker : glorialu this is go worker : glorialu this is go worker : glorialu this is go worker : glorialu this is go worker : glorialu this is go worker : glorialu this is go worker : glorialu this is go worker : glorialu this is go worker : glorialu this is go worker : glorialu main finished

如果不用協程，上面代碼應該三個線程運行，分別是主函數main和 兩個函數。 使用協程之后，實際運行兩個線程，這就是并發的好處。

Note：當使用go啟動協程之后,這2個函數就被切換到協程里面執行了，但是這時候主線程結束了，這2個協程還沒來得及執行就會掛了！所以不在main中加time進行sleep就無法看到協程中的執行結果。

• 多次運行，其結果可能如下：

this is go worker : glorialu this is go worker : glorialu this is go worker : glorialu this is go worker : glorialu this is go worker : glorialu this is go worker : glorialu this is go worker : glorialu this is go worker : glorialu this is go worker : glorialu this is go worker : glorialu this is go worker : lineshen this is go worker : lineshen this is go worker : lineshen this is go worker : lineshen this is go worker : lineshen this is go worker : lineshen this is go worker : lineshen this is go worker : lineshen this is go worker : lineshen this is go worker : lineshen main finished

會發現lineshen和 glorialu 的順序不是固定的，這進一步說明了一個問題，那就是多個協程是同時執行的。不過睡眠這種做法肯定是不靠譜的，go 自帶一個WaitGroup可以解決這個問題,。

• WaitGroup示例如下：

package mainimport ("fmt""time""sync") var wg sync.WaitGroupfunc go_worker(name string) {for i:=0; i<10; i++ {fmt.Println("this is go worker :" , name)}wg.Done() }func main(){wg.Add(2)go go_worker("lineshen")go go_worker("glorialu")wg.Wait()// time.Sleep(time.Second*5) // print effectivefmt.Println("main finished") }

sync.WaitGroup也起到了time.Sleep的效果。但是協程內部的執行順序是不確定的。

sync.WaitGroup用法: var 是聲明了一個全局變量 wg，類型是sync.WaitGroup，wg.Add(2) 指2個goroutine需要執行，
wg.Done 相當于 wg.Add(-1) 意思就是該協程執行結束；wg.Wait()通信主線程wait，等2個協程都執行完再退出。

應用實例：從３個庫取不同的數據匯總處理，最簡單寫法就是查３次庫，但是這３次查詢必須按順序執行，大部分編程語言的代碼執行順序都是從上到下，假如一個查詢耗時１s，３個查詢就是３s，但是使用協程你可以讓這３個查詢同時進行，也就是１s就可以搞定。

2. Golang協程池與channel機制

• 同類型channel

如何將協程中結果返回給主線程？golang提供了channel機制。示例如下：

package mainimport ("fmt""sync") var wg sync.WaitGroupfunc go_worker(name string, ch chan string) {for i:=0; i<10; i++ {ch <- name}wg.Done() }func main(){wg.Add(2)ch := make(chan string)go go_worker("lineshen", ch)go go_worker("glorialu", ch)for {fmt.Println("this is go worker :" , <-ch)}wg.Wait()fmt.Println("main finished") }

代碼執行結果如下。就是實例化了一個channel，go啟動的協程同時向這個2個管道輸出數據，主線程使用了一個for循環從管道里面取數據。其實就是一個生產者-消費者模式，與redis隊列有點像。下面也可以看到lineshen和glorialu進入管道的順序是不固定的。如果實驗發現輸出順序固定的，那是因為電腦跑的太快了，可以把循環開的大一點。

this is go worker : glorialu this is go worker : glorialu this is go worker : lineshen this is go worker : glorialu this is go worker : lineshen this is go worker : glorialu this is go worker : lineshen this is go worker : glorialu this is go worker : lineshen this is go worker : glorialu this is go worker : lineshen this is go worker : glorialu this is go worker : lineshen this is go worker : glorialu this is go worker : lineshen this is go worker : glorialu this is go worker : lineshen this is go worker : glorialu this is go worker : lineshen this is go worker : lineshen fatal error: all goroutines are asleep - deadlock!

也看到發生了致命的錯誤：fatal error: all goroutines are asleep - deadlock! 所有的協程都睡眠了，程序監測到死鎖！go的channel默認是阻塞的(假如不設置緩存)，需要“放一個-取一個”。如果channel里面放置的數據沒有取出來，程序就會一直等下去，死鎖了；同時，如果channel里面沒有放置數據，主線程去取數據也會發生死鎖！

如何解決這個問題呢？標準的做法是主動關閉管道，或者知道應該什么時候關閉管道。對于示例代碼，可以簡單加入一個計數器判斷何時channel中的數據可以完全被取出。如下：

package mainimport ("fmt""sync") var wg sync.WaitGroupfunc go_worker(name string, ch chan string) {for i:=0; i<10; i++ {ch <- name}wg.Done() }func main(){wg.Add(2)ch := make(chan string)go go_worker("lineshen", ch)go go_worker("glorialu", ch)counter := 1for {fmt.Println("this is go worker :" , <-ch)if counter >= 20 {close(ch)break}counter++}wg.Wait()fmt.Println("main finished") }

輸出如下：

this is go worker : glorialu this is go worker : glorialu this is go worker : lineshen this is go worker : glorialu this is go worker : lineshen this is go worker : glorialu this is go worker : lineshen this is go worker : glorialu this is go worker : lineshen this is go worker : glorialu this is go worker : lineshen this is go worker : glorialu this is go worker : lineshen this is go worker : glorialu this is go worker : lineshen this is go worker : glorialu this is go worker : lineshen this is go worker : glorialu this is go worker : lineshen this is go worker : lineshen main finished

• 多種類型channel，使用select進行判斷

package mainimport ("time""fmt")func go_worker1_int(ch chan int) {for i:=0; ; i++ {ch <- itime.Sleep(time.Duration(time.Second))} }func go_worker2_string(name string, ch chan string){for i:=0; ; i++ {ch <- nametime.Sleep(time.Duration(time.Second))} } func go_worker3_print(ch1 chan int, ch2 chan string){chRate := time.Tick(time.Duration(time.Second))for {select {case v := <-ch1:fmt.Printf("Received on channel 1: %d\n", v)case v := <-ch2:fmt.Printf("Received on channel 2: %s\n", v)case <-chRate:fmt.Printf("log...\n")}} }func main(){ch1 := make(chan int)ch2 := make(chan string)go go_worker1_int(ch1)go go_worker2_string("lineshen", ch2)go_worker3_print(ch1, ch2)time.Sleep(time.Duration(time.Second*10))fmt.Println("main finished") }

輸出結果如下：

Received on channel 1: 0 Received on channel 2: lineshen Received on channel 1: 1 Received on channel 2: lineshen log... Received on channel 2: lineshen Received on channel 1: 2 log... log... Received on channel 1: 3 Received on channel 2: lineshen log... Received on channel 1: 4 Received on channel 2: lineshen log...

該程序建立了2個管道一個傳輸int，一個傳輸string，同時啟動了3個協程，前2個協程非常簡單，就是每隔1s向管道輸出數據，第三個協程是不停的從管道取數據，并通過定時器功能可以每隔一段時間向管道輸出內容！

不同的是，go_worker1_int和go_worker2_string是2個不同的管道，通過select可以實現在不同管道之間切換，哪個管道有數據就從哪個管道里面取數據，如果都沒數據就等著。

總結

以上是生活随笔為你收集整理的Go协程与协程池的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。