CognitoIdentityCredentials return session undefined about react-native-aws-cognito-js HOT 1 CLOSED

const cognitoUser = new CognitoUser(userData);
cognitoUser.authenticateUser(authenticationDetails, {
  onSuccess: (result) => {
    console.log('access token + ' + result.getAccessToken().getJwtToken());
    Config.credentials = new CognitoIdentityCredentials({
      IdentityPoolId: appConfig.IdentityPoolId,
      Logins: {
        [`cognito-idp.${appConfig.region}.amazonaws.com/${appConfig.UserPoolId}`]: result.getIdToken().getJwtToken()
      }
    });
    alert('Success');
    console.log(Config.credentials);
    //now user is logged in - can get session here
    cognitoUser.getSession((error, result) => {
      if (error) {
        console.log(error);
      } else {
        console.log(result);
      }
    });
  },
  onFailure: (err) => {
    alert(err);
  },
});