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package main

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

func main() {
	tick := time.NewTicker(1 * time.Second)
	var i int
	for {
		fmt.Println("当前 Goroutine 数量:", runtime.NumGoroutine())
		<-tick.C
		fmt.Println("tick:", i)
		time.Sleep(3 * time.Second)
		i++
		println(i)
		fmt.Println(time.Now())
		if i == 5 {
			break
		}

	}

}

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// A Ticker holds a channel that delivers “ticks” of a clock
// at intervals.
type Ticker struct {
	C <-chan Time // The channel on which the ticks are delivered.
	r runtimeTimer
}

// NewTicker returns a new Ticker containing a channel that will send
// the current time on the channel after each tick. The period of the
// ticks is specified by the duration argument. The ticker will adjust
// the time interval or drop ticks to make up for slow receivers.
// The duration d must be greater than zero; if not, NewTicker will
// panic. Stop the ticker to release associated resources.
func NewTicker(d Duration) *Ticker {
	if d <= 0 {
		panic("non-positive interval for NewTicker")
	}
	// Give the channel a 1-element time buffer.
	// If the client falls behind while reading, we drop ticks
	// on the floor until the client catches up.
	c := make(chan Time, 1)
	t := &Ticker{
		C: c,
		r: runtimeTimer{
			when:   when(d),
			period: int64(d),
			f:      sendTime,
			arg:    c,
		},
	}
	startTimer(&t.r)
	return t
}

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// /usr/local/Cellar/go/1.21.6/libexec/src/runtime/time.go
// startTimer adds t to the timer heap.
//
//go:linkname startTimer time.startTimer
func startTimer(t *timer) {
	if raceenabled {
		racerelease(unsafe.Pointer(t))
	}
	addtimer(t)
}


// Note: this changes some unsynchronized operations to synchronized operations
// addtimer adds a timer to the current P.
// This should only be called with a newly created timer.
// That avoids the risk of changing the when field of a timer in some P's heap,
// which could cause the heap to become unsorted.
func addtimer(t *timer) {
	// when must be positive. A negative value will cause runtimer to
	// overflow during its delta calculation and never expire other runtime
	// timers. Zero will cause checkTimers to fail to notice the timer.
	if t.when <= 0 {
		throw("timer when must be positive")
	}
	if t.period < 0 {
		throw("timer period must be non-negative")
	}
	if t.status.Load() != timerNoStatus {
		throw("addtimer called with initialized timer")
	}
	t.status.Store(timerWaiting)

	when := t.when

	// Disable preemption while using pp to avoid changing another P's heap.
	mp := acquirem()

	pp := getg().m.p.ptr()
	lock(&pp.timersLock)
	cleantimers(pp)
	doaddtimer(pp, t)
	unlock(&pp.timersLock)

	wakeNetPoller(when)

	releasem(mp)
}