in src/main/java/com/awslabs/aws/iot/websockets/BasicMqttOverWebsocketsProvider.java [91:94]
private void setUsernamePassword(ImmutableUsernamePassword usernamePassword, MqttConnectOptions connOpts) {
usernamePassword.getUsername().ifPresent(connOpts::setUserName);
usernamePassword.getPassword().ifPresent(connOpts::setPassword);
}