Use _stop_event consistently across all threads as the way to signal that it should stop. Add thread joins with timeouts to allow the program to exit cleanly

providers/solarconditions/giroionosonde.py

@@ -67,11 +67,15 @@ class GIROIonosonde(SolarConditionsProvider):
 
     def start(self):
         logger.info(f"Set up query of GIRO ionosonde data API every {POLL_INTERVAL} seconds.")
-        self._thread = Thread(target=self._run, name="GIROIonosondeDataProvider")
+        self._thread = Thread(target=self._run, name="GIROIonosondeDataProvider", daemon=True)
         self._thread.start()
 
     def stop(self):
         self._stop_event.set()
+        if self._thread:
+            self._thread.join(timeout=35)
+            if self._thread.is_alive():
+                logger.warning("GIRO ionosonde worker thread did not exit on time and will be killed.")
 
     def _run(self):
         # Real interval at which we poll is the "once per hour" divided by the number of stations, so each one gets