How to write struct onto ledger state

I am trying to write chaincode for Hyperledger that has a mapping, that stores struct values mapped to strings. This is my first time writing contracts for Hyperledger and also my first time using go and it appears I am not approaching this the right way.

This is my mapping, Data struct, Init function and addVData function that shows the problem.

type Data struct{
    Timestamp string
    Velocity string
    Location string
}

var all_data map[string]Data

func (t *DataContract) Init(stub shim.ChaincodeStubInterface) peer.Response {
    all_data = make(map[string]Data)

    return shim.Success(nil)
}


func (t *DataContract) addVData(stub shim.ChaincodeStubInterface, args []string) peer.Response {
    params := stub.GetStringArgs()
    fmt.Println("The params passed in are:", params)

    if len(params) != 4 {
        fmt.Println("Please resubmit in this particular order: addVData, Timestamp, Velocity, Location")
        return shim.Error("Please resubmit in this particular order: addVData, Timestamp, Velocity, Location")
    }

    var d = Data{Timestamp:params[1], Velocity:params[2], Location:params[3]}
    all_data[params[1]] = d

    var err = stub.PutState(params[1],d)

    return shim.Success(nil)
}

The error I am getting is actually very clear:

./data.go:79:35: cannot use d (type Data) as type []byte in argument to stub.PutState

I am wondering, since my data is not in form of a byte array, how do I go about storing it? Also, I am not certain I have implemented the Init method and the mappings in the correct way but have had a hard time finding examples. If you could please explain and point me in the right direction it would be very appreciated, thank you.

Use json.Marshal function to convert the struct into bytes

type UserData struct {
 a string
}


userdata := &UserData{a: "hello"}

// Mashelling struct to jsonByte object to put it into the ledger
userDataJSONBytes, err := json.Marshal(&userdata)
if err != nil {
    return shim.Error(err.Error())
}

var err = stub.PutState(params[1],userDataJSONBytes)