There is a race condition when you want to reuse Timer instance with Reset method.

timer_race.go

package main

import "time"

func main() {

	for i := 0; i < 10000; i++ {
		timer := time.NewTimer(time.Microsecond)
		time.Sleep(time.Microsecond)
		flat := false
		if !timer.Stop() {
			select {
			case <-timer.C:
			default:
				flat = true
			}
		}

		if flat {
			timer.Reset(5 * time.Second)
			select {
			case <-timer.C:
				println("hello") // this will print immediately
			}
		}
	}
}