Go 中 time.After 可能导致的内存泄露问题解析

 func NewTimer(d Duration) *Timer
  // NewTimer 创建一个新的 Timer，它将至少持续时间 d 之后，在向通道中发送当前时间
  // d 表示间隔时间
 type Timer struct {
  	C <-chan Time
	r runtimeTimer
  }

func (t *Timer) Reset(d Duration) bool

if !t.Stop() {
	<-t.C
}
t.Reset(d)

func (t *Timer) Stop() bool
// 如果定时器已经过期或停止，返回 false，否则返回 true

if !t.Stop() {
 <-t.C
}

func NewTicker(d Duration) *Ticker

func After(d Duration) <-chan Time

package main
import (
	"fmt"
	"time"
)
func main() {
	ticker := time.NewTicker(time.Second)
	defer ticker.Stop()
	done := make(chan bool)
	go func() {
		time.Sleep(10 * time.Second)
		done <- true
	}()
	for {
		select {
		case <-done:
			fmt.Println("Done!")
			return
		case t := <-ticker.C:
			fmt.Println("Current time: ", t)
		}
	}
}

// https://GitHub.com/golang/go/blob/go1.20.4/src/time/sleep.go#LL156C1-L158C2
func After(d Duration) <-chan Time {
	return NewTimer(d).C
}
// Https://github.com/golang/go/blob/go1.20.4/src/time/sleep.go#LL50C1-L53C2
type Timer struct {
	C <-chan Time
	r runtimeTimer
}

package main
import (
	"fmt"
	"time"
)
func main() {
	ch1 := make(chan string, 1)
	go func() {
		time.Sleep(time.Second * 2)
		ch1 <- "hello"
	}()
	select {
	case res := <-ch1:
		fmt.Println(res)
	case <-time.After(time.Second * 1):
		fmt.Println("timeout")
	}
}

package main
import (
	"fmt"
	"net/http"
	_ "net/http/pprof"
	"time"
)
func main() {
	fmt.Println("start...")
	ch1 := make(chan string, 120)
	go func() {
		// time.Sleep(time.Second * 1)
		i := 0
		for {
			i++
			ch1 <- fmt.Sprintf("%s %d", "hello", i)
		}
	}()
	go func() {
		// http 监听8080, 开启 pprof
		if err := http.ListenAndServe(":8080", nil); err != nil {
			fmt.Println("listen failed")
		}
	}()
	for {
		select {
		case _ = <-ch1:
			// fmt.Println(res)
		case <-time.After(time.Minute * 3):
			fmt.Println("timeout")
		}
	}
}

// https://github.com/golang/go/blob/go1.20.4/src/time/sleep.go#LL150C1-L158C2
// After waits for the duration to elapse and then sends the current time
// on the returned channel. 
// It is equivalent to NewTimer(d).C.
// The underlying Timer is not recovered by the garbage collector
// until the timer fires. If efficiency is a concern, use NewTimer
// instead and call Timer.Stop if the timer is no longer needed.
func After(d Duration) <-chan Time {
	return NewTimer(d).C
}
// 在经过 d 时段后，会发送值到通道上，并返回通道。
// 底层就是 NewTimer(d).C。
// 定时器Timer启动前不会被垃圾回收器回收，定时器执行后才会被回收。
// 如果担心效率问题，可以使用 NewTimer 代替，如果不需要定时器可以调用 Timer.Stop 停止定时器。

package main
import (
	"fmt"
	"net/http"
	_ "net/http/pprof"
	"time"
)
func main() {
	fmt.Println("start...")
	ch1 := make(chan string, 120)
	go func() {
		// time.Sleep(time.Second * 1)
		i := 0
		for {
			i++
			ch1 <- fmt.Sprintf("%s %d", "hello", i)
		}
	}()
	go func() {
		// http 监听8080, 开启 pprof
		if err := http.ListenAndServe(":8080", nil); err != nil {
			fmt.Println("listen failed")
		}
	}()
	// time.After 放到 for 外面
	timeout := time.After(time.Minute * 3)
	for {
		select {
		case _ = <-ch1:
			// fmt.Println(res)
		case <-timeout:
			fmt.Println("timeout")
			return
		}
	}
}

package main
import (
	"fmt"
	"net/http"
	_ "net/http/pprof"
	"time"
)
func main() {
	fmt.Println("start...")
	ch1 := make(chan string, 120)
	go func() {
		// time.Sleep(time.Second * 1)
		i := 0
		for {
			i++
			ch1 <- fmt.Sprintf("%s %d", "hello", i)
		}
	}()
	go func() {
		// http 监听8080, 开启 pprof
		if err := http.ListenAndServe(":8080", nil); err != nil {
			fmt.Println("listen failed")
		}
	}()
	duration := time.Minute * 2
	timer := time.NewTimer(duration)
	defer timer.Stop()
	for {
		timer.Reset(duration) // 这里加上 Reset()
		select {
		case _ = <-ch1:
			// fmt.Println(res)
		case <-timer.C:
			fmt.Println("timeout")
			return
		}
	}
}