diff --git a/core/apiimpl.go b/core/apiimpl.go
index 402f0fb..13610d2 100644
--- a/core/apiimpl.go
+++ b/core/apiimpl.go
@@ -128,14 +128,14 @@ func (sub *subTavern) Invite(w http.ResponseWriter, r *http.Request) {
 		Invitee bson.M `bson:"invitee"`
 	}
 	if err := readBsonDoc(r.Body, &reqdoc); err != nil {
-		logger.Error("Invite failed. readBsonDoc returns err :", err)
+		logger.Println("Invite failed. readBsonDoc returns err :", err)
 		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
 
 	result, err := group.Invite(gid, mid, reqdoc.Inviter, reqdoc.Invitee)
 	if err != nil {
-		logger.Error("Invite failed. group.Invite returns err :", err)
+		logger.Println("Invite failed. group.Invite returns err :", err)
 		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
@@ -191,7 +191,7 @@ func (sub *subTavern) AcceptInvitation(w http.ResponseWriter, r *http.Request) {
 
 	err := group.AcceptInvitation(gid, mid, member)
 	if err != nil {
-		logger.Error("AcceptInvitation failed. group.AcceptInvitation returns err :", err)
+		logger.Println("AcceptInvitation failed. group.AcceptInvitation returns err :", err)
 		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
diff --git a/core/group_memory.go b/core/group_memory.go
index fcdebfb..31ba010 100644
--- a/core/group_memory.go
+++ b/core/group_memory.go
@@ -21,10 +21,12 @@ import (
 type accountID = primitive.ObjectID
 type ticketID = primitive.ObjectID
 type groupID = primitive.ObjectID
-type Body = bson.M
 
 func init() {
 	gob.Register(memberDoc{})
+	gob.Register(groupDoc{})
+	gob.Register(Invitation{})
+	gob.Register(InvitationFail{})
 }
 
 func makeTid(gid groupID, in accountID) string {
@@ -44,33 +46,51 @@ type Invitation struct {
 
 // 플레이어한테 공유하는 멤버 정보
 type memberDoc struct {
-	Body         `json:",inline"`
-	Invite       bool  `json:"_invite"`
-	InviteExpire int64 `json:"_invite_exp"`
+	Body         bson.M `json:"_body"`
+	Invite       bool   `json:"_invite"`
+	InviteExpire int64  `json:"_invite_exp"`
 }
 
 type InvitationFail bson.M
 
 type groupDoc struct {
-	Body     `json:",inline"`
+	Body     bson.M                `json:"_body"`
 	Members  map[string]*memberDoc `json:"_members"`
 	InCharge string                `json:"_incharge"`
+	Gid      string                `json:"_gid"`
 
-	rh    *RedisonHandler
-	id    groupID
-	idhex string
+	rh *RedisonHandler
+	id groupID
 }
 
-type groupDocWithId struct {
-	*groupDoc `json:",inline"`
-	Gid       string `json:"_gid"`
+func (p groupDoc) MarshalJSON() ([]byte, error) {
+	if len(p.Gid) == 0 {
+		p.Gid = p.id.Hex()
+	}
+
+	// Turn p into a map
+	type groupDoc_ groupDoc // prevent recursion
+	b, _ := json.Marshal(groupDoc_(p))
+
+	var m map[string]json.RawMessage
+	_ = json.Unmarshal(b, &m)
+
+	// Add tags to the map, possibly overriding struct fields
+	for k, v := range p.Body {
+		// if overriding struct fields is not acceptable:
+		// if _, ok := m[k]; ok { continue }
+		b, _ = json.Marshal(v)
+		m[k] = b
+	}
+
+	return json.Marshal(m)
 }
 
 func (gd *groupDoc) strid() string {
-	if len(gd.idhex) == 0 {
-		gd.idhex = gd.id.Hex()
+	if len(gd.Gid) == 0 {
+		gd.Gid = gd.id.Hex()
 	}
-	return gd.idhex
+	return gd.Gid
 }
 
 func (gd *groupDoc) tid(in accountID) string {
@@ -282,11 +302,8 @@ func (gm *groupInMemory) Invite(gid groupID, mid accountID, inviterDoc bson.M, i
 
 		gm.sendUpstreamMessage(&wshandler.UpstreamMessage{
 			Target: "@" + mid.Hex(),
-			Body: groupDocWithId{
-				groupDoc: gd,
-				Gid:      gd.strid(),
-			},
-			Tag: []string{"GroupDocFull"},
+			Body:   gd,
+			Tag:    []string{"GroupDocFull"},
 		})
 	}
 
@@ -296,11 +313,10 @@ func (gm *groupInMemory) Invite(gid groupID, mid accountID, inviterDoc bson.M, i
 	}
 
 	// 초대 중 표시
-	success, err := gm.rh.SetNX(gm.rh.ctx, targetid.Hex(), mid.Hex(), time.Duration(gm.InviteExpire)*time.Second).Result()
+	_, err = gm.rh.SetNX(gm.rh.ctx, targetid.Hex(), mid.Hex(), time.Duration(gm.InviteExpire)*time.Second).Result()
 	if err != nil {
 		return "", err
 	}
-	logger.Println("invitation key :", targetid.Hex(), success)
 
 	// invitee에게 알림
 	gm.sendUpstreamMessage(&wshandler.UpstreamMessage{
@@ -358,20 +374,18 @@ func (gm *groupInMemory) AcceptInvitation(gid groupID, mid accountID, member bso
 			return err
 		}
 
-		logger.Println(full)
-		var temp []groupDoc
+		var temp []*groupDoc
 		err = json.Unmarshal([]byte(full.(string)), &temp)
 		if err != nil {
 			return err
 		}
 
+		test, _ := json.Marshal(temp[0])
+		logger.Println(string(test))
 		gm.sendUpstreamMessage(&wshandler.UpstreamMessage{
 			Target: "@" + mid.Hex(),
-			Body: groupDocWithId{
-				groupDoc: &temp[0],
-				Gid:      gd.strid(),
-			},
-			Tag: []string{"GroupDocFull"},
+			Body:   temp[0],
+			Tag:    []string{"GroupDocFull"},
 		})
 	}