func (*DefaultTime) AfterFunc(d time.Duration, f func()) Timer {
	return time.AfterFunc(d, f)
}
AfterFunc waits for the duration to elapse and then calls f in its own
goroutine. It returns a Timer that can be used to cancel the call using its
Stop method.
package ttime
import "time"
type Time interface {
	Now() time.Time
	Sleep(d time.Duration)
	After(d time.Duration) <-chan time.Time
	AfterFunc(d time.Duration, f func()) Timer
}
type Timer interface {
	Reset(d time.Duration) bool
	Stop() bool
}
type DefaultTime struct{}
func (*DefaultTime) Now() time.Time {
	return time.Now()
}
func (*DefaultTime) Sleep(d time.Duration) {
	time.Sleep(d)
}
func (*DefaultTime) After(d time.Duration) <-chan time.Time {
	return time.After(d)
}