How to Properly Terminate a Goroutine When Using a Ticker Channel in Golang?

Ticker Channel Behavior in Golang

If you iterate over a ticker channel and call Stop(), the channel will pause but not close. This can lead to goroutines remaining active indefinitely.

Case Example:

Consider the following code snippet:

package main

import (
    "fmt"
    "time"
)

func main() {
    ticker := time.NewTicker(1 * time.Second)
    go func() {
        for _ = range ticker.C {
            fmt.Println("tick")
        }
    }()
    time.Sleep(3 * time.Second)
    fmt.Println("stopping ticker")
    ticker.Stop()
    time.Sleep(3 * time.Second)
}

Output:

2013/07/22 14:26:53 tick
2013/07/22 14:26:54 tick
2013/07/22 14:26:55 tick
2013/07/22 14:26:55 stopping ticker

As you can see, despite stopping the ticker, the goroutine continues to iterate indefinitely because the channel is not closed.

Solution:

One way to ensure the goroutine terminates is to use a second channel as follows:

package main

import (
    "fmt"
    "log"
    "time"
)

// Run the function every tick
// Return false from the func to stop the ticker
func Every(duration time.Duration, work func(time.Time) bool) chan bool {
    ticker := time.NewTicker(duration)
    stop := make(chan bool, 1)

    go func() {
        defer log.Println("ticker stopped")
        for {
            select {
            case time := <-ticker.C:
                if !work(time) {
                    stop <- true
                }
            case <-stop:
                return
            }
        }
    }()

    return stop
}

func main() {
    stop := Every(1*time.Second, func(time.Time) bool {
        fmt.Println("tick")
        return true
    })

    time.Sleep(3 * time.Second)
    fmt.Println("stopping ticker")
    stop <- true
    time.Sleep(3 * time.Second)
}

In this code:

• The Every function creates two channels: a ticker channel and a stop channel.
• The goroutine iterates over both channels.
• If the work function returns false, the stop channel is notified, causing the goroutine to exit.
• When Stop() is called, it sends a message to the stop channel, which terminates the goroutine.

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