detect when the connection with the server is closed when publishing with udp (#6)

examples/client-publish-udp.go

@@ -62,4 +62,8 @@ func main() {
 			break
 		}
 	}
+
+	// wait until the connection is closed
+	err = conn.LoopUDP()
+	fmt.Println("connection is closed (%s)", err)
 }