class SocketdClientChannel extends ChannelBase implements Channel {
    public static final SocketdClientChannel instance = new SocketdClientChannel();

    private final Map<String, SocketdChannel> channelMap = new HashMap<>();
    private final ReentrantLock SYNC_LOCK = new ReentrantLock();

    private SocketdChannel get(String hostname, String url) {<FILL_FUNCTION_BODY>}

    @Override
    public Result call(Context ctx) throws Throwable {
        pretreatment(ctx);

        URI uri = URI.create(ctx.url);
        String hostname = uri.getAuthority();
        SocketdChannel channel = get(hostname, ctx.url);

        return channel.call(ctx);
    }
}

        SocketdChannel channel = channelMap.get(hostname);

        if (channel == null) {
            SYNC_LOCK.lock();
            try {
                channel = channelMap.get(hostname);

                if (channel == null) {
                    try {
                        Session session = (Session) SocketD.createClient(url)
                                .listen(SocketdProxy.socketdToHandler)
                                .openOrThow();
                        channel = new SocketdChannel(() -> session);
                        channelMap.put(hostname, channel);
                    } catch (RuntimeException e) {
                        throw e;
                    } catch (Exception e) {
                        throw new IllegalStateException(e);
                    }
                }
            } finally {
                SYNC_LOCK.unlock();
            }
        }

        return channel;
    
<methods>public non-sealed void <init>() <variables>