golang channel select

尝试多个channel同时触发时，select的表现：

package main

import (
    "fmt"
    "time"
)

func loop(ch chan int){
    for i := 0; i < 10; i++ {
        ch <- i
    }
    close(ch)
}

func main() {
    ch1 := make(chan int, 100)
    ch2 := make(chan int, 100)
    
    go loop(ch1)
    go loop(ch2)
    
    for{
        select{
            case j, ok := <- ch2:
                if false == ok {
                    goto End
                }
                fmt.Println("ch2", j)
                
            case i,ok := <- ch1:
                if false == ok {
                    goto End
                }
                fmt.Println("ch1", i)
                
            case <-time.After(5 * time.Second):
                fmt.Println("time's up")
                goto End
        }
    }
    
    End:
    fmt.Println("finish!")
    
}

输出

ch1 0
ch1 1
ch1 2
ch1 3
ch1 4
ch1 5
ch1 6
ch1 7
ch1 8
ch1 9
finish!

package main

import (
    "fmt"
    "time"
)

func loop(ch chan int){
    for i := 0; i < 10; i++ {
        ch <- i
    }
    close(ch)
}

func main() {
    ch1 := make(chan int, 100)
    ch2 := make(chan int, 100)
    
    go loop(ch2)//把ch2的调度提到前面
    go loop(ch1)
    
    for{
        select{
            case j, ok := <- ch2:
                if false == ok {
                    goto End
                }
                fmt.Println("ch2", j)
                
            case i,ok := <- ch1:
                if false == ok {
                    goto End
                }
                fmt.Println("ch1", i)
                
            case <-time.After(5 * time.Second):
                fmt.Println("time's up")
                goto End
        }
    }
    
    End:
    fmt.Println("finish!")
    
}

输出：

ch2 0
ch2 1
ch2 2
ch2 3
ch2 4
ch2 5
ch2 6
ch2 7
ch2 8
ch2 9
finish!

package main

import (
    "fmt"
    "time"
    "runtime"
)

func loop(ch chan int){
    for i := 0; i < 10; i++ {
         runtime.Gosched()//给别的goroutine让渡出一些调度时间
        ch <- i
    }
    close(ch)
}

func main() {
    ch1 := make(chan int, 100)
    ch2 := make(chan int, 100)
    
    go loop(ch2)
    go loop(ch1)
    
    for{
        select{
            case j, ok := <- ch2:
                if false == ok {
                    goto End
                }
                fmt.Println("ch2", j)
                
            case i,ok := <- ch1:
                if false == ok {
                    goto End
                }
                fmt.Println("ch1", i)
                
            case <-time.After(5 * time.Second):
                fmt.Println("time's up")
                goto End
        }
    }
    
    End:
    fmt.Println("finish!")
    
}

输出：

ch2 0
ch1 0
ch2 1
ch1 1
ch2 2
ch1 2
ch2 3
ch1 3
ch2 4
ch1 4
ch2 5
ch1 5
ch2 6
ch1 6
ch2 7
ch1 7
ch2 8
ch1 8
ch2 9
finish!