elector & locker were failing to send out when not leader (#688)

* elector & locker were failing to send out when not leader

* update test to confirm non-active elector/locker are checked

* clean up data race

* try to make test more reliable

examples/elector/main.go

@@ -0,0 +1,73 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"time"
+
+	"github.com/go-co-op/gocron/v2"
+)
+
+var _ gocron.Elector = (*myElector)(nil)
+
+type myElector struct {
+	num    int
+	leader bool
+}
+
+func (m myElector) IsLeader(_ context.Context) error {
+	if m.leader {
+		log.Printf("node %d is leader", m.num)
+		return nil
+	}
+	log.Printf("node %d is not leader", m.num)
+	return fmt.Errorf("not leader")
+}
+
+func main() {
+	log.SetFlags(log.LstdFlags | log.Lmicroseconds)
+
+	for i := 0; i < 3; i++ {
+		go func(i int) {
+			elector := &myElector{
+				num: i,
+			}
+			if i == 0 {
+				elector.leader = true
+			}
+
+			scheduler, err := gocron.NewScheduler(
+				gocron.WithDistributedElector(elector),
+			)
+			if err != nil {
+				log.Println(err)
+				return
+			}
+
+			_, err = scheduler.NewJob(
+				gocron.DurationJob(time.Second),
+				gocron.NewTask(func() {
+					log.Println("run job")
+				}),
+			)
+
+			if err != nil {
+				log.Println(err)
+				return
+			}
+			scheduler.Start()
+
+			if i == 0 {
+				time.Sleep(5 * time.Second)
+				elector.leader = false
+			}
+			if i == 1 {
+				time.Sleep(5 * time.Second)
+				elector.leader = true
+			}
+		}(i)
+	}
+
+	select {} // wait forever
+}