How to use glib-networking to carry out a HTTP POST to a https URL?

Question

I'm trying to write a function to carry out a HTTP POST request to a https:// URL.

So far my code is:

    GError *error = NULL;
    GSocketClient *client = NULL;
    GTlsConnection *tls_conn = NULL;
    GSocketConnection *conn = NULL;
    GIOStream *iostream = NULL;
    GInputStream *input_stream = NULL;
    GOutputStream *output_stream = NULL;
    gsize bytes_read;
    gsize response_length = 0;

    // Create a GSocketClient for HTTPS
    client = g_socket_client_new();
    g_socket_client_set_tls(client, TRUE);

    // Connect to the server
    conn = g_socket_client_connect_to_uri(client, url, 443, NULL, &error);
    if (!conn) {
        g_error("Failed to connect: %s", error->message);
        g_clear_error(&error);
        goto cleanup;
    }

    // Get input and output streams
    input_stream = g_io_stream_get_input_stream(G_IO_STREAM(conn));
    output_stream = g_io_stream_get_output_stream(G_IO_STREAM(conn));

    // Send the POST request
    g_output_stream_write(output_stream, data, strlen(data), NULL, &error);
    if (error) {
        g_error("Failed to send POST data: %s", error->message);
        g_clear_error(&error);
        goto cleanup;
    }
    printf("Sent POST\n");
    // Read the response
    gchar response_data[4096];
    while ((bytes_read = g_input_stream_read(input_stream, &response_data, 4096, NULL, &error)) > 0) {
        response_length += bytes_read;
    }

url and data are gchar*s passed to this function from the caller. I can copy/paste url and data and use them successfully with curl from the command line, so I know those are valid. I see the "Sent POST" printf output at stdout, but unfortunately the call to g_input_stream_read() never returns.

I haven't been able to find any good clear examples of how this should work, hopefully someone can point out my error. Thanks!