The code makes it pretty clear a value is never sent on a channel, but here's a playground example:

https://play.golang.org/p/2OSQiHS4Zt5

Code:

func NewTimer(d Duration) *Timer {
        c := make(chan Time, 1)
        t := &Timer{    
                C: c,
                r: runtimeTimer{
                        when: when(d),
                        f:    sendTime,  // <<<<<<<<<<<<<<<<<<
                        arg:  c,
                },                      
        }                       
        startTimer(&t.r)
        return t        
}                       

vs

func AfterFunc(d Duration, f func()) *Timer {
        t := &Timer{
                r: runtimeTimer{
                        when: when(d),
                        f:    goFunc, // <<<<<<<<<<<<<<<<<<
                        arg:  f,
                },
        }       
        startTimer(&t.r)
        return t
}               

Context: review comments on https://go-review.googlesource.com/c/go/+/137335

We should probably say something about AfterFunc in the Timer.Reset docs.

Agreed.

My parsing of the Reset documentation was that the f parameter to AfterFunc being executed is equivalent to a value being received from t.C, and I figured that t.C gets received internally by AfterFunc to call f (or an equivalent mechanism).

However, it'd be great to be explicit and more accurate.

If Reset returns true, the function passed to AfterFunc will not be called. If Reset returns false, the function has already been called in a separate goroutine.

What about changing:

Reset should be invoked only on stopped or expired timers with drained channels.

to:

For a timer created with NewTimer, Reset should be invoked only on stopped or expired timers with drained channels.

?

If we're going to change something we may as well explain what happens with a timer created by time.AfterFunc.

Change https://golang.org/cl/285632 mentions this issue: time: clarify Timer.Reset behavior on AfterFunc Timers