Unlock() before panic() when already closed.

mq/lib.go

@@ -73,6 +73,7 @@ type state[T any] struct {
 func (s *state[T]) Close() {
 	s.mu.Lock()
 	if s.closed {
+		s.mu.Unlock()
 		panic("close of closed queue")
 	}
 	s.closed = true