chore: split executable into lib and main

gameserver/src/lib.rs

@@ -0,0 +1,12 @@
+#![feature(let_chains)]
+use anyhow::Result;
+
+mod net;
+mod util;
+
+use net::gateway::Gateway;
+
+pub async fn start_gameserver() -> Result<()> {
+    let mut gateway = Gateway::new("0.0.0.0", 23301).await?;
+    Box::pin(gateway.listen()).await
+}