diff --git a/example/src/custom_appender_tokio.rs b/example/src/custom_appender_tokio.rs
index e58f33f..8f24379 100644
--- a/example/src/custom_appender_tokio.rs
+++ b/example/src/custom_appender_tokio.rs
@@ -9,7 +9,7 @@ struct CustomLog {
 }
 
 impl LogAppender for CustomLog {
-    fn do_logs(&self, records: &[FastLogRecord]) {
+    fn do_logs(&mut self, records: &[FastLogRecord]) {
         let mut datas = String::new();
         for record in records {
             let now = DateTime::from(record.now);