go select with <-time.After(duration) first time instant

Question

at the moment I am using a for loop like this

for ; true; <-time.After(duration)

the first time it is executed instantly, then by <-time.After(duration)

Now I need to rewrite this function so that I can stop it with a channel. By default, this is done using select, but it waits for the <-time.After(duration) already at the first iteration

for {
    select {
    case <-done:
        return
    case t := <-time.After(duration):
        fmt.Println("Tick at", t)
    }
}

how i can solve it?

Answer 1

The select statement will cycle through the different channels checking one by one if the channel is ready for read or write.

In case no channel is ready for read or write, the select statement will block waiting for one of the channels readiness unless there is a default statement which in your case should be a no-op:

for {
    select {
    case <-done:
        return
    case t := <-time.After(duration):
        fmt.Println("Tick at", t)
    default: // cycle back
    }
}

Answer 2

Initially set zero delay and then change it on first execution

duration := DESIRED_DURATION * 0
for {
    select {
    case <-done:
        return
    case t := <-time.After(duration):
        duration = DESIRED_DURATION 
        fmt.Println("Tick at", t)
    }
}