func CloneEvent(ev Event, at time.Time) Event {
	ev.at = at
	return ev
}
CloneEvent event returns a copy of the event with the time adjusted to at.
package core
import (
	"fmt"
	"time"
	"golang.org/x/tools/internal/event/label"
)
type Event struct {
	at time.Time
	static  [3]label.Label  
	dynamic []label.Label   
}
type eventLabelMap struct {
	event Event
}
func (ev Event) At() time.Time { return ev.at }
func (ev Event) Format(f fmt.State, r rune) {
	if !ev.at.IsZero() {
		fmt.Fprint(f, ev.at.Format("2006/01/02 15:04:05 "))
	}
	for index := 0; ev.Valid(index); index++ {
		if l := ev.Label(index); l.Valid() {
			fmt.Fprintf(f, "\n\t%v", l)
		}
	}
}
func (ev Event) Valid(index int) bool {
	return index >= 0 && index < len(ev.static)+len(ev.dynamic)
}
func (ev Event) Label(index int) label.Label {
	if index < len(ev.static) {
		return ev.static[index]
	}
	return ev.dynamic[index-len(ev.static)]
}
func (ev Event) Find(key label.Key) label.Label {
	for _, l := range ev.static {
		if l.Key() == key {
			return l
		}
	}
	for _, l := range ev.dynamic {
		if l.Key() == key {
			return l
		}
	}
	return label.Label{}
}
func MakeEvent(static [3]label.Label, labels []label.Label) Event {
	return Event{
		static:  static,
		dynamic: labels,
	}
}