Hey! Thank you for answer. InstanceId is sample field. I have over 100 different message types and want to reflect json to different golang structs (I use switch evnvelope.Type ... json.Unmarshal(envelope.Json, &concreteType)...) I don't want json:"InstanceId"

And this is a bug with json.RawMessage

EDIT: yeah misread. Re-opening.

Same problem with marshaling. I marshal {Type, some_message} data and get some_message only without __type ))

https://play.golang.org/p/SsgQmtq2yP0

Hi @gromas,

Referring to your first example:

	bytes := []byte(`
		{"__type":"instance.started","InstanceId":"a9ff34dd-d20b-4887-99d6-f2f3a68f86a5"}
	`)
	
	var envelope struct {
		Type string `json:"__type"`
		Json *json.RawMessage
	}

What exactly do you expect to appear in the Json struct field?

@gromas
The go struct structure has to match the json structure, you cannot just dump all the unrecognized fields into a json.RawMessage
What you can do is unmarshal twice, once to find the type, second time into a known struct. json.RawMessage is for making this more convenient in more deeply nested structs

Your second example you are embedding a json.RawMessage whose MarshalJSON/UnmarshalJSON is being promoted to envelope and overriding the marshal process

Thanks @seankhliao. I'm going to close this issue, as it is not clear that this is a bug. @gromas, please see one of the resources on https://golang.org/wiki/Questions for further help using the encoding/json package.