// at a time. This is implemented using channels rather than a mutex.
type _Exclusive[Val any] struct {
	c chan Val
}

// _MakeExclusive makes an initialized exclusive value.
func _MakeExclusive[Val any](initial Val) *_Exclusive[Val] {
	r := &_Exclusive[Val]{
		c: make(chan Val, 1),
	}
	r.c <- initial
	return r
}