JSON encode in golang fabric chaincode behavior

[msalimbene]

I've seen several articles with similar errors, but none seems to work for me. I've seen the marbles samples, as well as many others, and still can't pinpoint the error.

I'm in fabric 2.x. The chaincode below works just fine when saving data, but fails when reading with the following message:

ERROR] Error submitting transaction: No valid responses from any peers. Errors:
    peer=org1peer-api.127-0-0-1.nip.io:8080, status=500, message=Error handling success response. Value did not match schema:
1. return: Additional property field1 is not allowed
2. return: Additional property field2 is not allowed
3. return: field1,omitempty is required
4. return: field2,omitempty is required

type Asset struct {
	Field1 string `json:"field1,omitempty"`
	Field2 string `json:"field2,omitempty"`
}

func (c *AssetContract) CreateAsset(ctx contractapi.TransactionContextInterface, assetID string, values string) (bool, error) {
	
	// convert json input to byte array
	txData := []byte(values)

	// convert byte array to HlpAsset struct
	asset := new(asset)
	err = json.Unmarshal(txData, &asset)

	// convert struct back to bytes
	txBytes, err := json.Marshal(asset)

	return true, ctx.GetStub().PutState(assetID, txBytes)
}

func (c *AssetContract) ReadAsset(ctx contractapi.TransactionContextInterface, assetID string) (*Asset, error) {

	txBytes, _ := ctx.GetStub().GetState(assetID)

	// convert byte array to HlpAsset struct
	asset := new(Asset)
	err = json.Unmarshal(txBytes, &asset)

	return asset, nil
}

testing with the following input data:

assetID: "3",
values: "{\"field1\":\"123\",\"field2\":\"a05\"}"

I found this question where this bug is mentioned:

Supplying additional valid data in JSON tag of struct property causes schema to fail.

The bug has been closed for around a year, however, I still experience that behavior. Overriding the JSON property using medatada didn't work either.

Using the struct like this worked perfectly:

type Asset struct {
	Field1 string `json:"field1"`
	Field2 string `json:"field2"`
}