add mutex to job (#74)

* add mutex to job

* go vet

job.go

@@ -2,11 +2,13 @@ package gocron
 
 import (
 	"fmt"
+	"sync"
 	"time"
 )
 
 // Job struct stores the information necessary to run a Job
 type Job struct {
+	sync.RWMutex
 	interval          uint64                   // pause interval * unit between runs
 	unit              timeUnit                 // time units, ,e.g. 'minutes', 'hours'...
 	startsImmediately bool                     // if the Job should run upon scheduler start
@@ -44,11 +46,13 @@ func NewJob(interval uint64) *Job {
 
 // Run the Job and immediately reschedule it
 func (j *Job) run() {
+	j.Lock()
+	defer j.Unlock()
 	callJobFuncWithParams(j.funcs[j.jobFunc], j.fparams[j.jobFunc])
 	j.runCount++
 }
 
-func (j Job) neverRan() bool {
+func (j *Job) neverRan() bool {
 	return j.lastRun.IsZero()
 }
 

scheduler.go

@@ -88,6 +88,8 @@ func (s *Scheduler) ChangeLocation(newLocation *time.Location) {
 
 // scheduleNextRun Compute the instant when this Job should run next
 func (s *Scheduler) scheduleNextRun(j *Job) {
+	j.Lock()
+	defer j.Unlock()
 	now := s.time.Now(s.loc)
 
 	if j.startsImmediately {

scheduler_test.go

@@ -252,17 +252,17 @@ func TestSwap(t *testing.T) {
 	s.Every(2).Minute().Do(task)
 
 	jb := s.Jobs()
-	var jobsBefore []Job
+	var jobsBefore []*Job
 	for _, p := range jb {
-		jobsBefore = append(jobsBefore, *p)
+		jobsBefore = append(jobsBefore, p)
 	}
 
 	s.Swap(1, 0)
 
 	jobsAfter := s.Jobs()
 
-	assert.Equal(t, &jobsBefore[0], jobsAfter[1])
-	assert.Equal(t, &jobsBefore[1], jobsAfter[0])
+	assert.Equal(t, jobsBefore[0], jobsAfter[1])
+	assert.Equal(t, jobsBefore[1], jobsAfter[0])
 }
 
 func TestLess(t *testing.T) {