Stream.getResponse() can hang because it calls join() without any timeout:

http://hg.openjdk.java.net/jdk9/dev/jdk/file/1049321b86cb/src/java.httpclient/share/classes/java/net/http/Stream.java

...
@Override
    HttpResponseImpl getResponse() throws IOException {
        try {
            return getResponseAsync(null).join();
        } catch (Throwable e) {
            Throwable t = e.getCause();
            if (t instanceof IOException) {
                throw (IOException)t;
            }
            throw e;
        }
    }
...

It can wait forever if a server just doesn't send anything. I also noticed that it may hang if a server send some incorrect response (the client continues waiting in this case).

It would be better if it took into account a timeout value specified for a connection, and threw HttpTimeoutException if timeout was reached.

Please see attached Timeout.java tests (timeout_test.tar) which reproduces the problem.