Updating data of struct to save in chaincode

Question

I have created a struct to store some data and i want to implement an update mechanism to it where the data in
the struct is update. I have tried the following code but its not working. How can i do it?

type Customer struct {
  UID     string
  Name    string
  Address struct {
    StreetNo string
    Country  string
  }
}
func (t *SimpleChaincode) update(stub shim.ChaincodeStubInterface, args []string) ([]byte, error) {

if len(args) != 2 {
    return nil, errors.New("Incorrect number of arguments. Expecting name of the key to query")
}
  //args[0] to get the UID of customer whose details to be updated
  //args[1] data that needs to be updated 

data,err:= stub.GetState(ars[0])
if err != nil {
     return nil, err
}
json.Unmarshal(data, &uid)
//append
data.Country= append(data.Country,args[1])
fmt.Printf("Risk Fag set for UID %s",data)

raw, err := json.Marshal(data)
  if err != nil {
     return nil, err
  }

  stub.PutState(data.UID, raw)

return nil,nil

}

Answer 1

You can use a code similar to this:
map[string]interface{}

byt := []byte(`{"num":6.13,"strs":["a","b"]}`)
if err := json.Unmarshal(byt, &dat); err != nil {
    panic(err)
}
fmt.Println(dat)

Go through the example of marshalling and unmarshalling structs from/to Json given in the following link:
https://github.com/hyperledger/fabric/blob/release/examples/chaincode/go/marbles02/marbles_chaincode.go