Timer and Callback Functions in Golang

Implement a timer based callback func in Golang

Program

package main
import (
 "fmt"
 "sync"
 "time"
)
type timerFunc func()
var timers *sync.Map
func startTimer(id string, callbackFunc timerFunc, timeout int) {
 if a, ok := timers.Load(id); ok {
  timer := a.(*time.Timer)
  timer.Stop()
  timers.Delete(id)
  // Delete from DB
  fmt.Println("===========  Existing Timer deleted ...", id)
 }
timer := time.NewTimer(time.Duration(timeout) * time.Second)
 fmt.Println("===========  Timer started ...", id)
 timers.Store(id, timer)
 // Add in DB
 go func() {
  <-timer.C
  fmt.Println("===========  Callback func calling ...", id)
  callbackFunc()
  fmt.Println("===========  Timer completed...", id)
  timers.Delete(id)
 }()
}
func stopTimer(id string) {
 if a, ok := timers.Load(id); ok {
  timer := a.(*time.Timer)
  timer.Stop()
  timers.Delete(id)
  // Delete from DB
  fmt.Println("===========  Timer deleted...", id)
 }
}
func a() {
 fmt.Println("===========  a called...")
}
func b() {
 fmt.Println("===========  b called...")
}
func main() {
 timers = new(sync.Map)
 fmt.Println("===========  Execution started")
 startTimer("id-a", a, 2)
 startTimer("id-b", b, 4)
 time.Sleep(8 * time.Second)
 startTimer("id-a", a, 4)
 startTimer("id-b", b, 4)
 time.Sleep(2 * time.Second)
 stopTimer("id-a")
 time.Sleep(100 * time.Second)
 fmt.Println("===========  Execution completed")
}

Output

===========  Execution started
===========  Timer started ... id-a
===========  Timer started ... id-b
===========  Callback func calling ... id-a
===========  a called...
===========  Timer completed... id-a
===========  Callback func calling ... id-b
===========  b called...
===========  Timer completed... id-b
===========  Timer started ... id-a
===========  Timer started ... id-b
===========  Timer deleted... id-a
===========  Callback func calling ... id-b
===========  b called...
===========  Timer completed... id-b
===========  Execution completed