fix(odbc): implement Drop for OdbcConnection to properly shut down worker threads

This prevents worker threads from hanging when ODBC connections are dropped,
allowing tests to exit properly instead of hanging indefinitely.

Author: lovasoa

sqlx-core/src/odbc/connection/mod.rs

@@ -64,3 +64,10 @@ impl Connection for OdbcConnection {
         false
     }
 }
+
+impl Drop for OdbcConnection {
+    fn drop(&mut self) {
+        // Send shutdown command to worker thread to prevent resource leak
+        self.worker.shutdown_sync();
+    }
+}

sqlx-core/src/odbc/connection/worker.rs

@@ -80,6 +80,16 @@ impl ConnectionWorker {
         send_command_and_await(&self.command_tx, Command::Shutdown { tx }, rx).await
     }
 
+    pub(crate) fn shutdown_sync(&mut self) {
+        // Send shutdown command without waiting for response
+        // Use try_send to avoid any potential blocking in Drop
+        let (tx, _rx) = oneshot::channel();
+        let _ = self.command_tx.try_send(Command::Shutdown { tx });
+
+        // Don't aggressively drop the channel to avoid SendError panics
+        // The worker thread will exit when it processes the Shutdown command
+    }
+
     pub(crate) async fn begin(&mut self) -> Result<(), Error> {
         let (tx, rx) = oneshot::channel();
         send_transaction_command(&self.command_tx, Command::Begin { tx }, rx).await
@@ -156,11 +166,12 @@ fn worker_thread_main(
     }
 
     // Process commands
-    for cmd in rx {
+    while let Ok(cmd) = rx.recv() {
         if !process_command(cmd, &conn) {
             break;
         }
     }
+    // Channel disconnected or shutdown command received, worker thread exits
 }
 
 fn establish_connection(options: &OdbcConnectOptions) -> Result<OdbcConnection, Error> {