Query result doesn't give the list of items, but just an empty array [ ] in aws-amplify - react-native

Question

I try to make a query to see the list of users. My custom lambda function (which I attached as policy) is as follows:
const aws = require('aws-sdk');
const ddb = new aws.DynamoDB();
exports.handler = async (event, context) => {
if (!event.request.userAttributes.sub) {
console.log("Error: No user was written to DynamoDB")
context.done(null, event);
return;
}
// Save the user to DynamoDB
const date = new Date();
const params = {
Item: {
'id': { S: event.request.userAttributes.sub },
'__typename': { S: 'User' },
'username': { S: event.userName },
'email': { S: event.request.userAttributes.email },
'createdAt': { S: date.toISOString() },
'updatedAt': { S: date.toISOString() },
},
TableName: process.env.USERTABLE,
}
try {
await ddb.putItem(params).promise();
console.log("Success");
} catch (e) {
console.log("Error", e);
}
context.done(null, event);
}
And the schema model is as follows:
type User #model
#auth(rules: [
{ allow: public, operations: [read]}
{ allow: owner }
])
{
id: ID!
username: String!
email: String!
}
Although there is one user in the dynamoDb, when I make a query by:
query listUsers {
listUsers {
items {
email
id
username
}
}
}
the result is as follows:
{
"data": {
"listUsers": {
"items": []
}
}
}
As can be seen, the array of "items" is empty, the items are not shown, when I look at the console dynamoDb table, I see user items with id, username and email values. But it should give the results, where do I make mistake? Meanwhile I am new on aws-amplify.