package main

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

// 来自文章 https://www.cnblogs.com/hwnd/p/20682814
func simulateRequest() {
	timeout := 500 * time.Millisecond
	ctx, cancel := context.WithDeadline(context.Background(), time.Now().Add(timeout))
	defer cancel()
	resultCh := make(chan string) // 无缓冲！

	// 启动 worker goroutine 处理"请求"
	go func() {
		time.Sleep(time.Duration(rand.Intn(500)+300) * time.Millisecond)
		select {
		case <-time.After(timeout):
			fmt.Println("worker 超时，放弃处理")
		case <-ctx.Done():
		case resultCh <- fmt.Sprintf("处理完成，耗时 %dms", rand.Intn(500)+300):

		}
	}()

	// TODO: 模拟请求取消或超时的情况（比如 500ms 后调用方不再关心结果）
	// 如果 worker 还没完成，它就 leak 了
	select {
	case resultCh := <-resultCh:
		fmt.Println(resultCh)
	case <-ctx.Done():
		fmt.Println("请求方取消了请求")
	}
}

func main() {
	for i := 0; i < 5; i++ {
		simulateRequest()
		fmt.Printf("第 %d 个请求处理完毕\n\n", i+1)
		time.Sleep(200 * time.Millisecond)
	}
	fmt.Println("所有请求处理完毕")
	// 运行后观察：goroutine 数量只增不减
	http.ListenAndServe(":6060", nil)
}