Go语言并发之Select多路选择操作符用法详解

package main
func main() {
	ch := make(chan int, 1)
	go func(chan int) {
		for {
			select {
			// 0或者1写入是随机的
			case ch <- 0:
			case ch <- 1:
			}
		}
	}(ch)
	for i := 0; i < 10; i++ {
		println(<-ch)
	}
}

select {
    case <-ch1 :     // 检测有没有数据可读
        // 一旦成功读取到数据，则进行该case处理语句
    case ch2 <- 1 :  // 检测有没有数据可写
        // 一旦成功向ch2写入数据，则进行该case处理语句
    default:
        // 如果以上都没有符合条件，那么进入default处理流程
}

package main
func main() {
	select {
	// 啥也不干，一直阻塞住
	}
}

select {
    case x, ok := <-ch1:
        ...
    case ch2 <- y:
        ...
    default:
        fmt.Println("default")
}

package main
import "fmt"
func main() {
	// 创建一个长度带缓冲的整型通道
	ch1 := make(chan int, 1)
	// 向通道中写入数据
	ch1 <- 1
	ch2 := make(chan int, 1)
	ch2 <- 2
	select {
	case <-ch1:
		fmt.Println("ch1 read")
	case <-ch2:
		fmt.Println("ch2 read")
	}
}

package main
import (
	"fmt"
	"time"
)
func main() {
	quit := make(chan bool)
	go func() {
		for {
			select {
			case <-quit:
				fmt.Println("quit")
				// 使用 return 就会退出整个goroutine线程；如果使用 break，程序仍然在for循环中执行
				return
			default:
				fmt.Println("default")
			}
		}
	}()
	time.Sleep(3 * time.Second)
	quit <- true // 主线程在3秒后，向quit信道写入数据
	time.Sleep(2 * time.Second)
	fmt.Println("main")
}

package main
import (
	"bufio"
	"fmt"
	"os"
)
// 通过控制台输入"bye",来控制main函数结束运行
func main() {
	quit := make(chan bool)
	ch := make(chan string)
	go func() {
		for {
			select {
			case name := <-ch:
				fmt.Printf("from main msg: [%v]\n", name)
				if name == "bye" {
					quit <- true
				} else {
					quit <- false
				}
			}
		}
	}()
	for {
		// 控制台输入
		fmt.Print("please input string: ")
		scanner := bufio.NewScanner(os.Stdin)
		scanner.Scan()
		ch <- scanner.Text()
		isOver := <-quit
		if isOver {
			break
		}
	}
	fmt.Println("main over")
}

package main
import (
	"fmt"
	"time"
)
func main() {
	quit := make(chan bool)
	ch := make(chan int)
	go func() {
		for {
			select {
			case num := <-ch:
				fmt.Println("num = ", num)
			case <-time.After(5 * time.Second):
				fmt.Println("超时")
				quit <- true
			}
		}
	}()
	for i := 0; i < 2; i++ {
		ch <- i
		time.Sleep(time.Second)
	}
	<-quit // 等待超时后, 结束 main主线程
	fmt.Println("程序结束")
}

package main
import (
	"fmt"
	"time"
)
func server1(ch chan string) {
	time.Sleep(6 * time.Second)
	ch <- "from server1"
}
func server2(ch chan string) {
	time.Sleep(3 * time.Second)
	ch <- "from server2"
}
func main() {
	output1 := make(chan string)
	output2 := make(chan string)
	go server1(output1)
	go server2(output2)
	s1 := <-output1
	fmt.Println(s1)
	s2 := <-output2
	fmt.Println(s2)
}

package main
import (
	"fmt"
	"time"
)
func server1(ch chan string) {
	time.Sleep(6 * time.Second)
	ch <- "from server1"
}
func server2(ch chan string) {
	time.Sleep(3 * time.Second)
	ch <- "from server2"
}
func main() {
	output1 := make(chan string)
	output2 := make(chan string)
	go server1(output1)
	go server2(output2)
	select {
	case s1 := <-output1:
		fmt.Println(s1)
	case s2 := <-output2:
		fmt.Println(s2)
	}
}

package main
import "time"
import (
	"fmt"
)
// select 管道参数并行
func server1(ch chan string) {
	time.Sleep(time.Second * 6)
	ch <- "response from server1"
}
func server2(ch chan string) {
	time.Sleep(time.Second * 3)
	ch <- "response from server2"
}
func main() {
	output1 := make(chan string)
	output2 := make(chan string)
	go server1(output1)
	go server2(output2)
	// 管道同时ready，select随机执行
	// time.Sleep(time.Second)
	select {
	case s1 := <-output1:
		fmt.Println("s1:", s1)
	case s2 := <-output2:
		fmt.Println("s2:", s2)
	default:
		fmt.Println("run default")
	}
}

package main
import (
	"fmt"
	"time"
)
func server1(ch chan string) {
	ch <- "from server1"
}
func server2(ch chan string) {
	ch <- "from server2"
}
func main() {
	output1 := make(chan string)
	output2 := make(chan string)
	go server1(output1)
	go server2(output2)
	time.Sleep(1 * time.Second)
	select {
	case s1 := <-output1:
		fmt.Println(s1)
	case s2 := <-output2:
		fmt.Println(s2)
	}
}