fix(#1517): stop background task when something happens to main thread (

#1519)

Closes #1517

(cherry picked from commit c610273)

src/rubrix/client/api.py

@@ -272,7 +272,11 @@ def log(
         )
         if background:
             return future
-        return future.result()
+
+        try:
+            return future.result()
+        finally:
+            future.cancel()
 
     async def log_async(
         self,