refactor: migrate net operation to KCP

gameserver/src/util.rs

@@ -6,3 +6,10 @@ pub fn cur_timestamp_ms() -> u64 {
         .unwrap()
         .as_millis() as u64
 }
+
+pub fn cur_timestamp_secs() -> u64 {
+    SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .unwrap()
+        .as_secs()
+}