Access the http response body before the entire response has been read

#include 
#include 
#include 
#include 
#include 
#include 
namespace net   = boost::asio;
namespace beast = boost::beast;
namespace http  = beast::http;
using boost::system::errorcode;
using net::ip::tcp;
tcp::socket sendget() {
    net::systemexecutor ex;
    tcp::socket          s(ex);
    connect(s, tcp::resolver(ex).resolve("httpbin.org", "http"));
    http::request req{http::verb::get, "/stream-bytes/2000?seed=42", 11};
    req.set(http::field::host, "httpbin.org");
    write(s, req);
    return s;
}
http::response usingstringbody() {
    tcp::socket conn = sendget();
    http::response res;
    beast::flat_buffer                buf;
    read(conn, buf, res);
    std::cerr