Ballerina Websocket client in main function

websocket_client.bal

import ballerina/io;
import ballerina/http;

public function main() {
    http:WebSocketClient wsClientEp = new("ws://echo.websocket.org", config = {callbackService: ClientService});
    checkpanic wsClientEp->pushText("hello");
}
service ClientService =@http:WebSocketServiceConfig {} service {

//This resource is triggered when a new text frame is received from the remote backend.
resource function onText(http:WebSocketClient conn, string text, boolean finalFrame) {
        io:println(text);
    }
};