我想知道<-Go 中函數(shù)的通道返回類型意味著什么。事實上，類型 T 的通道被寫為chan T并使用 來創(chuàng)建make(chan T, N)，那么 的<-返回類型中的“”意味著什么time.After？go doc time.Afterpackage time // import "time"func After(d Duration) <-chan Time    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.獎金：我如何看出go doc這time.After是異步的并且在持續(xù)時間過去之前不會阻塞？