Update task tutorial (#2)

* Add task package.

* Update task package.

* Make task package works as expected.

* Add task examples.

* Add task stats and error handler.

* Add Coordinator.

* Update coordinator.

* Bugs fix.

* Add more examples.

* Some fixes.

* Add test cases.

* Add go.sum.

* Change coordination implementation to setnx.

* Fix no at time periodic schedule.

* Limit job execution time; limit worker count.

* Add jobLock, add Remove and Clear job methods in scheduler.

* Add ClearJobs; Update OnceJob scheduler implementation.

* Add redis cluster support for coordinator.

* Move Coordinate to Run; add unit tests for Coordinate.

* Extract commonJob from OnceJob and PeriodicJob.

* unexport cron expression type.

* Add JobCount.

* Add timezone support in cron.

* Add Stop for Scheduler.

* Add coordinate for oncejob.

* extract coordinate to commonJob.

* Update unit tests.

* Add GetLatestScheduledTime.

* Move unit test into a separate package.

* Add start flag for scheduler.

* make some functions and methods unexported.

* Add examples for task.

* Change IntervalType to cronIntervalType.

* Add comments for exported items.

* Add task tutorial.

* Update README.

* Update README.

* Update go.sum.

* Update task tutorial.

Author: zhoufeng1989

task/README.md

@@ -12,6 +12,7 @@ Examples as below:
 package main
 
 import (
+    "time"
     "github.com/byte-power/gorich/task"
 )
 
@@ -49,6 +50,8 @@ You can also monitor the scheduled jobs via JobStats.
 package main
 
 import (
+    "fmt"
+    "time"
     "github.com/byte-power/gorich/task"
 )
 
@@ -65,13 +68,16 @@ func main() {
 }
 
 func monitorScheduler() {
-    // handle all job stats
-    allJobStats := task.JobStats()
-    for jobName, jobStats := range allJobStats {
-        fmt.Printf("job %s stat:\n", jobName)
-        for _, stat := range jobStats {
-            fmt.Println(stat.ToMap())
+    for {
+        // handle all job stats
+        allJobStats := task.JobStats()
+        for jobName, jobStats := range allJobStats {
+            fmt.Printf("job %s stat:\n", jobName)
+            for _, stat := range jobStats {
+                fmt.Println(stat.ToMap())
+            }
         }
+        time.Sleep(5 * time.Second)
     }
 }
 
@@ -90,6 +96,8 @@ Notice that Coordinate use a lock that will unlock automatically 5 seconds later
 package main
 
 import (
+    "fmt"
+    "time"
     "github.com/byte-power/gorich/task"
 )
 
@@ -110,27 +118,31 @@ func main () {
     go scheduler1.Start()
     go scheduler2.Start()
 
-    jobStats := job1.Stats()
-    fmt.Println("job1 stats:")
-    for _, stat := range jobStats {
-        fmt.Println(stat.ToMap())
-    }
+    go monitorJob(job1)
+    go monitorJob(job2)
 
-    jobStats = job2.Stats()
-    fmt.Println("job2 stats:")
-    for _, stat := range jobStats {
-        fmt.Println(stat.ToMap())
-    }
-    // stop schedulers after 10 seconds
-    time.Sleep(10 * time.Second)
+
+    // stop schedulers after 30 seconds
+    time.Sleep(30 * time.Second)
 
     scheduler1.Stop(false)
     scheduler2.Stop(false)
 }
 
+func monitorJob(job task.Job) {
+    for {
+        jobStats := job.Stats()
+        fmt.Printf("job  %s stats:\n", job.Name())
+        for _, stat := range jobStats {
+            fmt.Println(stat.ToMap())
+        }
+        time.Sleep(5 * time.Second)
+    }
+}
+
 func sum(a, b int) int {
     return a + b
 }
 ```
 
-See more examples [here](./example_test.go).
+See more examples [here](./example_test.go).