package main

import (
    "context"
    "fmt"
    "net/http"
    _ "net/http/pprof"
    "time"
)

func main() {
    go http.ListenAndServe(":8080",nil)
    ctx,_ := context.WithTimeout(context.Background(),(10 * time.Second))
    go testA(ctx)
    select {}
}

func testA(ctx context.Context) {
    ctxA,_ := context.WithTimeout(ctx,(1 * time.Second))
    ch := make(chan int)
    go testB(ctxA,ch)

    select {
    case <-ctx.Done():
        fmt.Println("testA Done")
        return
    case i := <-ch:
        fmt.Println(i)
    }

}

func testB(ctx context.Context,ch chan int) {
    //模拟读取数据
    sumCh := make(chan int)
    go func(sumCh chan int) {
        sum := 10
        time.Sleep(10 * time.Second)
        sumCh <- sum
    }(sumCh)

    select {
    case <-ctx.Done():
        fmt.Println("testB Done")
        <-sumCh
        return
    //case ch  <- <-sumCh: 注意这样会导致资源泄露
    case i := <-sumCh:
        fmt.Println("send",i)
        ch <- i
    }

}