type TxnCard struct {
        Iota           blockchain.Identity `json:"identity"`
        Theta   blockchain.TxnType  `json:"transaction_type"`
        Tau []int               `json:"valid_transactions"`
    }

    var foo TxnCard

    if err := json.Unmarshal(body, &foo); err != nil {
        panic(err)
    }
    fmt.Printf("+vn", foo)

{"identity":{"Address":"9934:4761:6a9d:b1eb:c7a5:4021:2ca6:1fac"},
"transaction_type":0,
"valid_transactions":[],
}

{Iota:�4Gaj���ǥ@!,��
Theta:0
Tau:[]
}