任务调度demo

• 模拟任务调度
• 同步(串行)任务/异步(并行)任务
• 遇到同步任务需执行完成后再执行后续任务

package main

import (
    "context"
    "fmt"
    "sync"
    "time"
)

func test(wg *sync.WaitGroup, ctx context.Context, jobId int) {
    defer wg.Done()
    for i := 0; i < 5; i++ {
        select {
        case <-ctx.Done():
            fmt.Printf("任务Id:%d,异常退出\n", jobId)
            return
        default:
            fmt.Printf("任务Id:%d,执行第%d次\n", jobId, i)
            if jobId > 2 {
                time.Sleep(time.Second * 5)
            } else {
                time.Sleep(time.Second * 2)
            }

        }
    }
}

func main() {
    ctx, cancel := context.WithCancel(context.Background())
    wg := new(sync.WaitGroup)
    go func() {
        time.Sleep(time.Second * 20)
        cancel()
    }()
    for i := 0; i < 5; i++ {
        wg.Add(1)
        go test(wg, ctx, i)

        if i < 1 {
            wg.Wait()
            select {
            case <-ctx.Done():
                fmt.Println("main1 异常退出")
                return
            default:
                fmt.Println("1 select")
            }
        }
    }
    wg.Wait()
    select {
    case <-ctx.Done():
        fmt.Println("main2 异常退出")
        return
    default:
        fmt.Println("2 select")
    }
    //测试阻塞
    select {}
}