Kronika - The keeper of time

Kronika adds some extra utility around the standard time package. It does not have any other external dependencies.

WaitUntil

kronika.WaitUntil(ctx context.Context, t time.Time)

WaitUntil will block until the given time. Unlike using time.After or time.Timer, it can be cancelled by cancelling the context.

WaitFor

kronika.WaitFor(ctx context.Context, diff time.Duration)

WaitFor will block for the specified duration. Unlike using time.After or time.Timer, it can be cancelled by cancelling the context.

Every

kronika.Every(ctx context.Context, start time.Time, interval time.Duration) <-chan time.Time

kronika.Every() works like a cron job. It is supplied a start time, and an interval, and it will send the current time to the returned channel at the specified intervals. Again, it can always be cancelled using the context.

Here are some examples of using Every

Run on Tuesdays by 2pm

ctx := context.Background()

start, err := time.Parse(
    "2006-01-02 15:04:05",
    "2019-09-17 14:00:00",
) // is a tuesday
if err != nil {
    panic(err)
}

interval := time.Hour * 24 * 7 // 1 week

for t := range kronika.Every(ctx, start, interval) {
    // Perform action here
    log.Println(t.Format("2006-01-02 15:04:05"))
}

Run every hour, on the hour

ctx := context.Background()

start, err := time.Parse(
    "2006-01-02 15:04:05",
    "2019-09-17 14:00:00",
) // any time in the past works but it should be on the hour
if err != nil {
    panic(err)
}

interval := time.Hour // 1 hour

for t := range kronika.Every(ctx, start, interval) {
    // Perform action here
    log.Println(t.Format("2006-01-02 15:04:05"))
}

Run every 10 minutes, starting in a week

ctx := context.Background()

// see https://golang.org/pkg/time/#Time.AddDate
start, err := time.Now().AddDate(0, 0, 7) 
if err != nil {
    panic(err)
}

interval := time.Minute * 10 // 10 minutes

for t := range kronika.Every(ctx, start, interval) {
    // Perform action here
    log.Println(t.Format("2006-01-02 15:04:05"))
}