fix golint issues in core/jsontype (#489)

core/jsontype/time.go

@@ -7,14 +7,17 @@ import (
 	"github.com/globalsign/mgo/bson"
 )
 
+// MilliTime represents time.Time that works better with mongodb.
 type MilliTime struct {
 	time.Time
 }
 
+// MarshalJSON marshals mt to json bytes.
 func (mt MilliTime) MarshalJSON() ([]byte, error) {
 	return json.Marshal(mt.Milli())
 }
 
+// UnmarshalJSON unmarshals data into mt.
 func (mt *MilliTime) UnmarshalJSON(data []byte) error {
 	var milli int64
 	if err := json.Unmarshal(data, &milli); err != nil {
@@ -25,14 +28,17 @@ func (mt *MilliTime) UnmarshalJSON(data []byte) error {
 	return nil
 }
 
+// GetBSON returns BSON base on mt.
 func (mt MilliTime) GetBSON() (interface{}, error) {
 	return mt.Time, nil
 }
 
+// SetBSON sets raw into mt.
 func (mt *MilliTime) SetBSON(raw bson.Raw) error {
 	return raw.Unmarshal(&mt.Time)
 }
 
+// Milli returns milliseconds for mt.
 func (mt MilliTime) Milli() int64 {
 	return mt.UnixNano() / int64(time.Millisecond)
 }