fix golint issues in core/load (#495)

core/load/sheddergroup.go

@@ -6,11 +6,13 @@ import (
 	"github.com/tal-tech/go-zero/core/syncx"
 )
 
+// A ShedderGroup is a manager to manage key based shedders.
 type ShedderGroup struct {
 	options []ShedderOption
 	manager *syncx.ResourceManager
 }
 
+// NewShedderGroup returns a ShedderGroup.
 func NewShedderGroup(opts ...ShedderOption) *ShedderGroup {
 	return &ShedderGroup{
 		options: opts,
@@ -18,6 +20,7 @@ func NewShedderGroup(opts ...ShedderOption) *ShedderGroup {
 	}
 }
 
+// GetShedder gets the Shedder for the given key.
 func (g *ShedderGroup) GetShedder(key string) Shedder {
 	shedder, _ := g.manager.GetResource(key, func() (closer io.Closer, e error) {
 		return nopCloser{