add keepalive ping, onclose event reason

src/main.ts

@@ -159,6 +159,16 @@ ws.on("upgrade", () => {
   );
 });
 
+ws.on("close", (event: CloseEvent) => {
+  console.log(`Connection closed: ${event.reason}`);
+});
+
+ws.on("open", () => {
+  setInterval(() => {
+    ws.send(JSON.stringify({ type: "ping" }));
+  }, 20000);
+});
+
 ws.on("message", async (data) => {
   try {
     const message: WSEvent = JSON.parse(data.toString("utf-8"));