await semaphore.acquire()

app.py

@@ -78,8 +78,13 @@ async def generation(ctx, attachment, start_time):
     if attachment:
         style = 'JoJo'
 
-        with semaphore:
+        await semaphore.acquire()
+        try:
             im = await asyncio.get_running_loop().run_in_executor(None, jojogan.predict, attachment.url, style)
+            semaphore.release()
+        except Exception as e:
+            semaphore.release()
+            raise e
         #im = await asyncio.to_thread(jojogan.predict, attachment.url, style)
         #im = jojogan.predict(attachment.url, style)