Usage

auto client = ClientHTTPS::create("www.google.com", ioService);{  auto request = client->get("/");  {    request->onHeader([](const ErrorCode& ec, const Header& header) {      std::cout << "request onheader " << ec << std::endl;      std::cout << std::endl << "Header received; ec: " << ec << std::endl;      std::cout << header.field() << std::endl;    }).onBodyChunk([](const ErrorCode& ec, std::istream& is, std::size_t chunkSize) {      std::cout << "request onbodychunk chunksize: " << chunkSize << ", ec: " << ec << std::endl;      if (!ec) {        std::cout << std::endl << "Body chunk received; ec: " << ec << std::endl;        std::copy_n(std::istreambuf_iterator<char>{is}, chunkSize, std::ostreambuf_iterator<char>{std::cout});        std::cout << std::endl;        if (chunkSize == 0)// this is the last chunk          std::cout << "all chunks received" << std::endl;      }    }).onTimeout([]() {      std::cout << "timeout" << ec << std::endl;    }).onComplete([client, request](const ErrorCode& ec) {      std::cout << "oncomplete" << ec << std::endl;      ioService.stop();    });    client->schedule(request);  }}