Go Academy · Lesson

The robfig/cron Library

Schedule with cron syntax.

Lesson 2 of 413 steps

The robfig/cron Library is a free Go Academy lesson on CoddyKit. This is lesson 2 of 4. Any 3 lessons of this learning path are free to read in full — after that, CoddyKit PRO unlocks every lesson, plus hands-on practice with a built-in code editor and a 24/7 AI tutor. It is part of the Go Academy learning path, and your progress syncs across the web and the CoddyKit app. The Go Academy course includes 4 lessons in total.

Cron Expressions in Go

The robfig/cron library lets you schedule jobs with familiar cron syntax instead of hand-written time math. Install with go get github.com/robfig/cron/v3.

import "github.com/robfig/cron/v3"

Cron Syntax Refresher

A standard cron expression has five fields:

minute (0-59)
hour (0-23)
day of month (1-31)
month (1-12)
day of week (0-6)

Example: 0 9 * * 1-5 = 9:00 AM on weekdays.

Creating a Scheduler

cron.New() returns a scheduler. You add jobs, then start it.

c := cron.New()
c.Start()
defer c.Stop()

Adding a Job

AddFunc registers a function to run on a schedule, returning an entry ID and an error if the spec is invalid.

id, err := c.AddFunc("30 * * * *", func() {
    fmt.Println("runs at minute 30")
})
if err != nil {
    log.Fatal(err)
}
_ = id

The Seconds Field

robfig/cron v3 uses a 5-field spec by default (no seconds). To enable a 6-field spec with seconds, build the cron with the seconds option.

c := cron.New(cron.WithSeconds())
c.AddFunc("*/5 * * * * *", func() { fmt.Println("every 5s") })

Predefined Schedules

Convenient macros exist:

@hourly
@daily
@weekly
@every 1h30m

c.AddFunc("@every 1h30m", func() { fmt.Println("every 90 min") })
c.AddFunc("@daily", func() { fmt.Println("midnight") })

Removing Jobs

Use the returned EntryID to remove a job dynamically.

id, _ := c.AddFunc("@hourly", task)
// later:
c.Remove(id)

Jobs Run in Goroutines

Each scheduled job runs in its own goroutine. If a job can overlap with its next trigger, guard against concurrency or use a wrapper that skips overlapping runs.

Timezones

By default schedules use the machine's local time. Pass a location to make them explicit and avoid DST surprises.

loc, _ := time.LoadLocation("America/New_York")
c := cron.New(cron.WithLocation(loc))

Parsing Without Running

You can validate a spec or compute the next run with a parser, which is great for tests and showing users the next execution.

sched, _ := cron.ParseStandard("0 9 * * 1-5")
next := sched.Next(time.Now())
fmt.Println("next run:", next)

Runnable: Compute Next Cron Run (Analogy)

robfig/cron is external; this standard-library snippet models the simplest cron rule "every minute at minute boundary" by computing the next matching time.

package main

import (
    "fmt"
    "time"
)

func nextRun(from time.Time) time.Time {
    return from.Truncate(time.Minute).Add(time.Minute)
}

func main() {
    now := time.Date(2026, 1, 1, 8, 15, 30, 0, time.UTC)
    fmt.Println("now:", now.Format("15:04:05"))
    fmt.Println("next:", nextRun(now).Format("15:04:05"))
}

Quick Check

Test your understanding of the robfig/cron library.

Answer it in the interactive lesson

Recap

You learned the robfig/cron library:

cron.New() + AddFunc(spec, fn) + Start()
5-field spec by default; WithSeconds adds a seconds field
Macros like @daily and @every simplify common schedules
Use Remove, locations, and ParseStandard for control and testing

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Frequently Asked Questions

Is the “The robfig/cron Library” lesson free?

Yes — any 3 lessons of the Go Academy learning path, including “The robfig/cron Library”, are free to read in full here on the web. After that, CoddyKit PRO unlocks every lesson, plus interactive practice with a built-in code editor and a 24/7 AI tutor. The Go Academy course includes 4 lessons in total.

What will I learn in “The robfig/cron Library”?

Schedule with cron syntax. You practise Go Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Go Academy?

No prior experience is required. Go Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 2 of 4.

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