Timer.Reset and channel lifetime

[Wojciech Kaczmarek]

Hi Gophers.

I'm wondering if the Timer.C channel can be invalidated (recreated) after calling Reset.

In other words, is it safe to store the C channel on side after Timer creation and will it survive further calls of Reset.

I realize there was change in Go 1.23 with regard to GC-ing timers, but in this case, reference to the timer itself and its channel is held by the program so it is not garbage collected.

cheers,

Wojciech

 

[Amnon]

yes, Timer.C does not get invalidated on Reset.
You can store it as will, read from it, wait for it, and it will survive calls to Reset.

To test it, try something like this:

https://go.dev/play/p/PRDU0sg_uJ-?v=

package main

import (
"fmt"
"time"
)

func main() {
start := time.Now()
delay := time.Second
t := time.NewTimer(delay)
defer t.Stop()

for range t.C {
fmt.Println(time.Since(start))
delay *= 2
t.Reset(delay)
if delay > 16*time.Second {
return
}
}
}

[Wojciech Kaczmarek]

Thank you Amnon.

I was using similar tests, but I had suspicion I just might be lucky to not hit an underneath channel change.

OTOH, quick look at the runtime/time.go source seems to confirm the channel stays.