Invalid Lambda Response: Received invalid response from Lambda: Unrecognized field

i am working on Amazon lex. when i give input to amazon lex

**its gives me following error**


i add lambda function in Fulfillment and from lambda i am getting customer information from MySQL Database

**here is my lambda function**

`const mysql = require('mysql');
var pool = mysql.createPool({ // a connection pool is a cache of database connections maintained so that the connections can be reused when future requests to the database are required
host: process.env.RDS_HOSTNAME,
user: process.env.RDS_USERNAME,
password: process.env.RDS_PASSWORD,
port: process.env.RDS_PORT,
database: process.env.RDS_DATABASE
});

exports.handler = (event, context, callback) => {

let MembershipNumber = event.currentIntent.slots.MembershipNumber;

// allows for using callbacks as finish/error-handlers
context.callbackWaitsForEmptyEventLoop = false;
pool.getConnection(function(err, connection) {
if (err) throw err;
let sql = "select * from Sales.CustomerTable where MembershipNumber= ? LIMIT 1";
let field = [MembershipNumber];
connection.query(sql,field, function (err, result, fields) {
if (err) {
console.log(err); // an error occurred
context.fail(buildResponse(false));
}
else {
if (result.length === 1) {
//console.log(data.Items[0].Arrival_city);
var FirstName = result[0].FirstName;
var LastName = result[0].LastName;
var Address = result[0].Address;
var PrimaryPhone = result[0].PrimaryPhone;
var SecondaryPhone = result[0].SecondaryPhone;
var Email = result[0].Email;
var Type = result[0].Type;
var MembershipNumber = result[0].MembershipNumber;
var Pin = result[0].Pin;
callback(null, {
"dialogAction": {
"type": "ConfirmIntent",
"fulfillmentState": "Fulfilled",
"message": {
"contentType": "PlainText",
"content": FirstName,LastName,Address,PrimaryPhone,SecondaryPhone,Email,Type,MembershipNumber,Pin
}
}
});
}
else {
console.log("Membership Number not found");
callback(null, buildResponse(true, "none"));
}
}
});
});
};
function buildResponse(isSuccess, FirstName, LastName, Address, PrimaryPhone, SecondaryPhone, Email, Type, MembershipNumber, Pin) {
if (isSuccess) {
return {
FirstName: FirstName,
LastName: LastName,
Address: Address,
PrimaryPhone: PrimaryPhone,
SecondaryPhone: SecondaryPhone,
Email:Email,
Type:Type,
MembershipNumber:MembershipNumber,
Pin:Pin,
lambdaResult: "success"
};
}
else {
console.log("Lambda returned error to Connect");
return { lambdaResult: "Error" };
}
}
`
**here is the test event object**

`{

"messageVersion": "1.0",
"invocationSource": "FulfillmentCodeHook",
"userId": "user-1",
"sessionAttributes": {},
"bot": {
"name": "Sales",
"alias": "sales",
"version": "$LATEST"
},
"outputDialogMode": "Text",
"currentIntent": {
"name": "iamamember",
"slots": {
"MembershipNumber": "78541258"
},
"confirmationStatus": "None"
}
}`

i want to integrate this with my contact flow. i don't what is this error about. If anyone of you know help me. Thanks