// that do an os.Setenv in main.init or main.main.
	asynctimerchan atomic.Int32
}

var dbgvars = []*dbgVar{
	{name: "adaptivestackstart", value: &debug.adaptivestackstart},
	{name: "asyncpreemptoff", value: &debug.asyncpreemptoff},
	{name: "asynctimerchan", atomic: &debug.asynctimerchan},
	{name: "cgocheck", value: &debug.cgocheck},
	{name: "clobberfree", value: &debug.clobberfree},

		default=go1.21
		panicnil=1
		asynctimerchan=0
	)

The special key `default` indicates a Go version to take unspecified
settings from. This allows setting the GODEBUG defaults separately
from the Go language version in the module.
In this example, the program is asking for Go 1.21 semantics and
then asking for the old pre-Go 1.21 `panic(nil)` behavior and the
new Go 1.23 `asynctimerchan=0` behavior.

	run(t, "NewTickerStop", func() { NewTicker(Hour).Stop() })
}

func TestChan(t *testing.T) {
	for _, name := range []string{"0", "1", "2"} {
		t.Run("asynctimerchan="+name, func(t *testing.T) {
			t.Setenv("GODEBUG", "asynctimerchan="+name)
			t.Run("Timer", func(t *testing.T) {
				tim := NewTimer(10000 * Second)
				testTimerChan(t, tim, tim.C, name == "0")
			})
			t.Run("Ticker", func(t *testing.T) {

	arg    any
	seq    uintptr

	// If non-nil, the timers containing t.
	ts *timers

	// sendLock protects sends on the timer's channel.
	// Not used for async (pre-Go 1.23) behavior when debug.asynctimerchan.Load() != 0.
	sendLock mutex
}

// init initializes a newly allocated timer t.
// Any code that allocates a timer must call t.init before using it.
// The arg and f can be set during init, or they can be nil in init

func reflect_chanrecv(c *hchan, nb bool, elem unsafe.Pointer) (selected bool, received bool) {
	return chanrecv(c, elem, !nb)
}

func chanlen(c *hchan) int {
	if c == nil {
		return 0
	}
	async := debug.asynctimerchan.Load() != 0
	if c.timer != nil && async {
		c.timer.maybeRunChan()
	}
	if c.timer != nil && !async {
		// timer channels have a buffered implementation
		// but present to users as unbuffered, so that we can