Unmarshalling Dynamic JSON Data With Overlapping Fields in Golang

Sorry If i'm posting a question that has already been answered, but I can't seem to find any similar situations on here. I have a websocket client that receives dynamic json data with overlapping fields. The fact that the fields overlap has has made Unmarshalling very difficult for me.

I have structs for the data types I receive, but I need a way to check the json data before I unmarshal it to a specific struct. I was hoping that an interface could act as a temporary holder and I would then be able to match the interface to the specific struct I want to unmarshal to, but that doesn't seem possible, or I just don't know how to go about it. Here are a few examples of the data types I'm receiving and structs to go along with it in case that helps.

response 1: {"connectionID":17973829270596587247,"event":"systemStatus","status":"online","version":"1.9.0"}
response 2: {"channelID":328,"channelName":"ohlc-5","event":"subscriptionStatus","pair":"XBT/USD","status":"subscribed","subscription":{"interval":5,"name":"ohlc"}}
response 3: [328,["1649576721.042916","1649577000.000000","42641.50000","42641.50000","42641.50000","42641.50000","42641.50000","0.00335101",2],"ohlc-5","XBT/USD"]
response 4: {"event":"heartbeat"}
structs below
import (
"time"
"encoding/json"
)
type ConnStatus struct {
ConnectionID		uint64			`json:"connectionID"`
Event				string			`json:"event"`
Status 				string			`json:"status"`
Version				string			`json:"version"`
}
type HeartBeat struct {
Event				string			`json:"event"`
}
type OHLCsuccess struct {
ChannelID			int				`json:"channelID"`
ChannelName			string			`json:"channelName"`
Event				string			`json:"event"`
Pair				string			`json:"pair"`
Status				string			`json:"status"`
Subscription		OHLC			`json:"subscription"`
}
type OHLC struct {
Interval		int			`json:"interval"`
Name			string		`json:"name"`
}
type OHLCUpdates struct {
ChannelID			int
OHLCArray			OHLCNewTrade
ChannelName			string
Pair				string
}
type OHLCNewTrade struct {
StartTime 			UnixTime
EndTime				UnixTime
Open				float64
High				float64
Low					float64
Close				float64
VWAP				float64
Volume				float64
Count				int
}
type UnixTime struct {
time.Time
}
func (u *UnixTime) UnmarshalJSON(d []byte) error {
var ts int64
err := json.Unmarshal(d, &ts)
if err != nil {
return err
}
u.Time = time.Unix(ts, 0).UTC()
return nil
}

Any idea(s) on how to go about this? Thanks in advance for the help!

Are you in control of the different responses? If so, wow about adding a "type" field to the top level?

See "How to put everything at the top level" section on https://eagain.net/articles/go-dynamic-json/ for more info.

E.g. (untested):

func UnmarshalJSON(d []byte) error {
	var jsonValue map[string]interface{}
	err := json.Unmarshal(d, &jsonValue)

	if err != nil {
		return err
	}

	switch jsonValue["type"] {
	case 1:
		// unmarshal into struct type 1
	case 2:
		// unmarshal into struct type 2
	default:
		// throw err
	}

	// or if you don't have access to type:
	if jsonValue["connectionID"] != nil {
		// unmarshal into struct type 1
	}

	return nil
}

Alternatively you could try to (strictly) unmarshal into each struct, until you don't get an error, e.g. something like:

func DetermineStruct(d []byte) int {
	var connStatus *ConnStatus

	reader := bytes.NewReader(d)
	decoder := json.NewDecoder(reader)
	decoder.DisallowUnknownFields()

	err := decoder.Decode(connStatus)
	if err == nil {
		panic(err)
	}

	err = json.Unmarshal(d, &connStatus)
	if err == nil {
		return 1
	}

	var ohlcSuccess OHLCsuccess
	err = json.Unmarshal(d, &ohlcSuccess)
	if err == nil {
		return 2
	}
}