function quit(): void {
        if($this->goingAway) {
            return;
        }
        
        $this->goingAway = \React\Promise\resolve();
        
        /** @var \Plasma\DriverInterface  $conn */
        foreach($this->connections->all() as $conn) {
            $conn->quit();
            $this->connections->delete($conn);
        }
        
        /** @var \Plasma\DriverInterface  $conn */
        foreach($this->busyConnections->all() as $conn) {
            $conn->quit();
            $this->busyConnections->delete($conn);
        }
    }