Configurable port

src/server.js

···
     });
   }
 
-  async start() {
-    this.app.listen(3000, () => {
-      console.log("Server is running on port 3000");
+  async start({ port }) {
+    this.app.listen(port, () => {
+      console.log(`Server is running on port ${port}`);
     });
     this.app.on("error", (error) => {
       console.error("Server error:", error);
···
 
 async function main() {
   const args = yargs(process.argv.slice(2)).parse();
+  const port = args.port ?? args.p ?? 3000;
   const configFilepath = args.config || "config.json";
   const config = await Config.fromFile(configFilepath);
   const handler = await Handler.fromConfig(config);
   const server = new Server({
     handler,
   });
-  await server.start();
+  await server.start({ port });
 }
 
 main();