fix golint issues in core/threading (#524)

core/threading/routinegroup.go

@@ -2,10 +2,12 @@ package threading
 
 import "sync"
 
+// A RoutineGroup is used to group goroutines together and all wait all goroutines to be done.
 type RoutineGroup struct {
 	waitGroup sync.WaitGroup
 }
 
+// NewRoutineGroup returns a RoutineGroup.
 func NewRoutineGroup() *RoutineGroup {
 	return new(RoutineGroup)
 }

core/threading/taskrunner.go

@@ -5,16 +5,19 @@ import (
 	"github.com/tal-tech/go-zero/core/rescue"
 )
 
+// A TaskRunner is used to control the concurrency of goroutines.
 type TaskRunner struct {
 	limitChan chan lang.PlaceholderType
 }
 
+// NewTaskRunner returns a TaskRunner.
 func NewTaskRunner(concurrency int) *TaskRunner {
 	return &TaskRunner{
 		limitChan: make(chan lang.PlaceholderType, concurrency),
 	}
 }
 
+// Schedule schedules a task to run under concurrency control.
 func (rp *TaskRunner) Schedule(task func()) {
 	rp.limitChan <- lang.Placeholder
 

core/threading/workergroup.go

@@ -1,10 +1,12 @@
 package threading
 
+// A WorkerGroup is used to run given number of workers to process jobs.
 type WorkerGroup struct {
 	job     func()
 	workers int
 }
 
+// NewWorkerGroup returns a WorkerGroup with given job and workers.
 func NewWorkerGroup(job func(), workers int) WorkerGroup {
 	return WorkerGroup{
 		job:     job,
@@ -12,6 +14,7 @@ func NewWorkerGroup(job func(), workers int) WorkerGroup {
 	}
 }
 
+// Start starts a WorkerGroup.
 func (wg WorkerGroup) Start() {
 	group := NewRoutineGroup()
 	for i := 0; i < wg.workers; i++ {