robfig/cron — Go cron library guide

package main

import (
    "log"
    "time"

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

func main() {
    c := cron.New(cron.WithLocation(time.UTC))

    c.AddFunc("0 9 * * 1-5", func() {
        log.Println("Weekday 09:00 UTC tick")
    })

    c.AddFunc("@hourly", func() {
        log.Println("Hourly tick")
    })

    c.Start()
    select {} // block forever
}

parser := cron.NewParser(
    cron.SecondOptional | cron.Minute | cron.Hour |
    cron.Dom | cron.Month | cron.Dow | cron.Descriptor,
)

c := cron.New(cron.WithParser(parser))

// 6-field with seconds (every 30 seconds):
c.AddFunc("*/30 * * * * *", everyThirtySeconds)

// Standard 5-field still works:
c.AddFunc("*/5 * * * *", everyFiveMinutes)

// Descriptor:
c.AddFunc("@daily", dailyTask)

type ReportJob struct {
    db *sql.DB
}

func (j *ReportJob) Run() {
    rows, _ := j.db.Query(...)
    // ...
}

c.AddJob("0 9 * * 1-5", &ReportJob{db: myDB})

AddJob accepts any type implementing cron.Job (a single Run() method). Useful when the job needs dependencies — pass them via the struct fields.

• Local timezone by default — pass cron.WithLocation(time.UTC) for UTC.
• Wraparound for `*/N` — same as Unix cron; */7 in the hour field doesn't divide 24 evenly.
• No `L` / `W` / `#` — use runtime checks or switch to github.com/adhocore/gronx / github.com/gorhill/cronexpr.
• Goroutine-per-job — long-running jobs don't block other ticks. If you need single-instance semantics, gate with a mutex or use cron.SkipIfStillRunning middleware.