actually update last_checked

src/fetch.rs

@@ -61,8 +61,9 @@ impl PdfFetcher {
             Err(_) => None,
         };
 
+        let now = Instant::now();
         if let Some(instant) = self.last_checked {
-            if Instant::now() - instant < *MIN_CHECK_INTERVAL {
+            if now - instant < *MIN_CHECK_INTERVAL {
                 return if cache_modtime.is_some() {
                     self.cached_pdf()
                 } else {
@@ -124,6 +125,7 @@ impl PdfFetcher {
             <dyn futures::Sink<bytes::Bytes, Error = std::io::Error> + Unpin>::close(&mut sink)
                 .await?;
         }
+        self.last_checked = Some(now);
         self.cached_pdf()
     }