Go Academy · Lesson

The robfig/cron Library

Schedule with cron syntax.

The robfig/cron Library is a free Go Academy lesson on CoddyKit — lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Go Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

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.

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

Frequently asked questions

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

Yes — the full text of “The robfig/cron Library” is free to read here on the web, and the Go Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Go Academy course, upgrade to CoddyKit PRO.

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; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “The robfig/cron Library” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Go Academy lesson?

Yes. Every Go Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

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