server.go
func (s *Server) StreamExists(id string) bool {
	s.mu.Lock()
	defer s.mu.Unlock()

	return s.Streams[id] != nil
}
func (s *Server) StreamExists(id string) bool {
	s.mu.Lock()
	defer s.mu.Unlock()

	return s.Streams[id] != nil
}
// StreamExists checks whether a stream by a given id exists