In encoding/json, there is MarshalJSON() and UnmarshaslJSON() for RawMessage. Missing this two method leads to different behavior while Marshal() jsoniter.RawMessage using std json package.
Example code below
```
package main
import (
 "fmt"
 "encoding/json"
 "github.com/json-iterator/go"
)
type T struct {
 Msg jsoniter.RawMessage
}
func main() {
 var j T
 
 raw := []byte(`{ "Msg": {"Foo": "Bar"}}`)
 
 jsoniter.Unmarshal(raw, &j)
 
 b1, _ := json.Marshal(j.Msg)
 fmt.Printf("%s\n", b1) /// Expect `{"Foo": "Bar"}` but got `"IHsiRm9vIjogIkJhciJ9"`
 
 b2, _ := jsoniter.Marshal(j.Msg)
 fmt.Printf("%s\n", b2)
}
```