refactor goctl, fix golint issues (#903)

core/contextx/unmarshaler_test.go

@@ -8,7 +8,6 @@ import (
 )
 
 func TestUnmarshalContext(t *testing.T) {
-
 	type Person struct {
 		Name string `ctx:"name"`
 		Age  int    `ctx:"age"`

core/mapping/unmarshaler.go

@@ -524,7 +524,6 @@ func (u *Unmarshaler) fillSliceValue(slice reflect.Value, index int, baseKind re
 			return errTypeMismatch
 		}
 
-
 		ithVal.Set(reflect.ValueOf(value))
 		return nil
 	}