CancelRequest: handle 'An existing connection was forcibly closed by the remote host' on Windows

Author: levakin

pgconn/pgconn.go

@@ -935,21 +935,30 @@ func (pgConn *PgConn) CancelRequest(ctx context.Context) error {
 	buf := make([]byte, 16)
 	binary.BigEndian.PutUint32(buf[0:4], 16)
 	binary.BigEndian.PutUint32(buf[4:8], 80877102)
-	binary.BigEndian.PutUint32(buf[8:12], uint32(pgConn.pid))
-	binary.BigEndian.PutUint32(buf[12:16], uint32(pgConn.secretKey))
-	_, err = cancelConn.Write(buf)
-	if err != nil {
-		return err
+	binary.BigEndian.PutUint32(buf[8:12], pgConn.pid)
+	binary.BigEndian.PutUint32(buf[12:16], pgConn.secretKey)
+
+	if _, err := cancelConn.Write(buf); err != nil {
+		return fmt.Errorf("write to connection for cancellation: %w", err)
 	}
 
-	_, err = cancelConn.Read(buf)
-	if err != io.EOF {
-		return err
+	if _, err := cancelConn.Read(buf); err != nil {
+		if errors.Is(err, io.EOF) || isConnectionClosedError(err) {
+			return nil
+		}
+
+		return fmt.Errorf("unexpected error while reading connection response: %w", err)
 	}
 
 	return nil
 }
 
+// isConnectionClosedError checks the error message to identify
+// the specific "forcibly closed" error that occurs on Windows.
+func isConnectionClosedError(err error) bool {
+	return strings.Contains(err.Error(), "An existing connection was forcibly closed by the remote host")
+}
+
 // WaitForNotification waits for a LISTON/NOTIFY message to be received. It returns an error if a notification was not
 // received.
 func (pgConn *PgConn) WaitForNotification(ctx context.Context) error {