Go - Encode nested structure

I'm working on an extension of http://gary.burd.info/go-websocket-chat.

This example sends raw text through websockets.

I want to use JSON data instead.

I did some structures in my Go code, but when I convert it to JSON to write it to the client, the nested structures are not in the result.

Some code :

type(
    ChatroomData struct {
    	Token string `json:"token"`
    	Chatroom *Chatroom `json:"chatroom"`
	}
	Message struct {
		Token string `json:"token,omitempty"`
    	Type string `json:"type"`
    	Author string `json:"author"`
	    Content string `json:"content"`
	    Chatroom string `json:"chatroom"`
    }
    Messages []Message
)

The chatroom struct :

Chatroom struct {
	Name string `json:"name"`
	Users []User `json:"users"`
	Messages Messages `json:"messages"`
	Hub *WsHub `json:"-"`
}
Chatrooms map[string]*Chatroom
User struct {
	username string `json:"username"`
	token string `json:"-"`
}
Users []User

Start the chatroom :

func (s *Server) startMainChatroom() {
    s.Chatrooms["main"] = &Chatroom{
	    Name: "main",
    	Users: make([]User, 0),
    	Messages: make([]Message, 0),
    	Hub: NewHub(),
    }
    go s.Chatrooms["main"].Hub.Run()
}

The way to append messages to the chatroom :

message := Message{}
json.Unmarshal([]byte(data), &message)
message.Token = ""
message.Type = "message"
chatroom.Messages = append(chatroom.Messages, message)

Send data to the client :

func (u *User) SendChatroomData(w http.ResponseWriter, c *Chatroom, status int) {
    chatroomData := ChatroomData{Token: u.token, Chatroom: c}

    w.Header().Set("Access-Control-Allow-Origin", "*")
    w.Header().Set("Access-Control-Allow-Headers", "accept, authorization")
    w.Header().Set("Access-Control-Allow-Methods", "GET, POST")
    w.WriteHeader(status)
    if err := json.NewEncoder(w).Encode(&chatroomData); err != nil {
    	panic(err)
    }
}

The printed result is :

{
     "token":"a638ed3ba0c30ba3d0810fc79e12a50a",
     "chatroom":{
         "name":"main",
         "users":[{},{}],
         "messages":[]
     }
}

There are two users and three messages were sent. If I use fmt.Printf("%v\n", chatroom.Messages), I have the three messages correctly stored. Same for the users, data is here when I dump it.

Many things are strange :

• Why the messages key stays empty ?
• Why the users key doesn't, but the slice items are empty ? (solved by Mike Reedell)

Thank you for your help, don't hesitate to ask me more code if it needs to be. I hope my post isn't already too long (and not too full of english errors X)) !

The go JSON marshaler will only output exported (capitalized) fields. The field in the User struct are un-exported (lower-case), which means the JSON marshaler doesn't know they are there and can't output them.

The problem was totally elsewhere : The Chatroom instance I used when adding some messages wasn't bound correctly to s.Chatrooms["main"], due to my misunderstanding of pointers.

When I marshaled s.Chatrooms["main"], the messages weren't inside !

Ty for your help !

I hope this will help some others go-learners