Golang: struct does not unmarshal int64 field correctly, other fields are correct

I have an http endpoint that receives some json that I unmarshal into a struct. All fields unmarshal correctly with the exception of an int64 timestamp field. There is no error, but the value is set to 0 instead of the value in the json. I tried changing to an int but got the same result.

The struct definition:

type BTMeta struct {
    IMEI string `json: "imei"`
    Timestamp int64 `json: "ts"`
    SignalStrength int `json: "signalStrength"`
    BatteryVoltage int `json: "batteryVoltage"`
}

type BTWeightValues struct {
    Unit int `json: "unit"`
    Tare int `json: "tare"`
    Weight uint `json: "weight"`
}

type BTWeight struct {
    BTMeta
    Values BTWeightValues `json: "values"`
}

The controller code (I removed error checking and irrelevant code):

func PostBTScale(res http.ResponseWriter, req *http.Request) {
    var data model.BTWeight
    _ := json.NewDecoder(req.Body).Decode(&data)
    log.Println(data.Timestamp)
    _ = database.DB.AddNewWeight(data)
    res.WriteHeader(http.StatusOK)
}

The JSON:

{
  "imei": "012896009462125",
  "ts": 1380562575798,
  "batteryVoltage": 5940,
  "signalStrength": 90,
  "values": {
    "unit": 1,
    "tare": 0,
    "weight": 61200
  },
  "rssi": 68,
  "deviceId": 12896009462125
}

Everything is correct after I unmarshal into a BTWeight except Timestamp is set to 0.

>Solution :

None of the JSON tags are working. The correct form of json tags are:

Timestamp int64 `json:"ts"`

Not

Timestamp int64 `json: "ts"`

That is, without the space after :.

It is working for other fields because field names match JSON keys.