More efficient clean_up of MessageCache

src/message.rs

@@ -50,24 +50,9 @@ impl MessageCache {
             let mut store = cache.store.lock().unwrap();
 
             let now = Instant::now();
-            let to_rm: Vec<String> = store
-                .iter()
-                .filter_map(|(entry, entrytime)| {
-                    if let Some(duration) = now.checked_duration_since(*entrytime) {
-                        if duration > MESSAGECACHEDURATION {
-                            Some(entry.clone())
-                        } else {
-                            None
-                        }
-                    } else {
-                        None
-                    }
-                })
-                .collect();
-
-            for key in to_rm {
-                store.remove(&key);
-            }
+            store.retain(|_, &mut entrytime| {
+                now.duration_since(entrytime) <= MESSAGECACHEDURATION
+            });
         }
     }
 }