dailyjob should not allow interval zero (#791)

Author: JohnRoesler

errors.go

@@ -9,6 +9,7 @@ var (
 	ErrDailyJobAtTimeNil             = fmt.Errorf("gocron: DailyJob: atTime within atTimes must not be nil")
 	ErrDailyJobAtTimesNil            = fmt.Errorf("gocron: DailyJob: atTimes must not be nil")
 	ErrDailyJobHours                 = fmt.Errorf("gocron: DailyJob: atTimes hours must be between 0 and 23 inclusive")
+	ErrDailyJobZeroInterval          = fmt.Errorf("gocron: DailyJob: interval must be greater than 0")
 	ErrDailyJobMinutesSeconds        = fmt.Errorf("gocron: DailyJob: atTimes minutes and seconds must be between 0 and 59 inclusive")
 	ErrDurationJobIntervalZero       = fmt.Errorf("gocron: DurationJob: time interval is 0")
 	ErrDurationRandomJobMinMax       = fmt.Errorf("gocron: DurationRandomJob: minimum duration must be less than maximum duration")

job.go

@@ -252,6 +252,10 @@ func (d dailyJobDefinition) setup(j *internalJob, location *time.Location, _ tim
 		return ErrDailyJobMinutesSeconds
 	}
 
+	if d.interval == 0 {
+		return ErrDailyJobZeroInterval
+	}
+
 	ds := dailyJob{
 		interval: d.interval,
 		atTimes:  atTimesDate,

scheduler_test.go

@@ -607,6 +607,17 @@ func TestScheduler_NewJobErrors(t *testing.T) {
 			nil,
 			ErrDailyJobMinutesSeconds,
 		},
+		{
+			"daily job interval 0",
+			DailyJob(
+				0,
+				NewAtTimes(
+					NewAtTime(1, 0, 0),
+				),
+			),
+			nil,
+			ErrDailyJobZeroInterval,
+		},
 		{
 			"weekly job at times nil",
 			WeeklyJob(