fix golint issues (#899)

core/mapping/unmarshaler.go

@@ -518,7 +518,8 @@ func (u *Unmarshaler) fillSliceValue(slice reflect.Value, index int, baseKind re
 			target.Set(reflect.ValueOf(value))
 			ithVal.Set(target.Addr())
 			return nil
-		} else {
+		}
+
 		if ithVal.Kind() != reflect.TypeOf(value).Kind() {
 			return errTypeMismatch
 		}
@@ -526,7 +527,6 @@ func (u *Unmarshaler) fillSliceValue(slice reflect.Value, index int, baseKind re
 		ithVal.Set(reflect.ValueOf(value))
 		return nil
 	}
-	}
 }
 
 func (u *Unmarshaler) generateMap(keyType, elemType reflect.Type, mapValue interface{}) (reflect.Value, error) {