The piso patch 1 (#590)

* Update httplib.h

When you disconnect and reconnect from the network, your network stack rewrites and updates /etc/resolv.conf accordingly. This configuration file is needed by the DNS resolver in the C library. The C library reads the DNS configuration from /etc/resolv.conf the first time, and caches it. It doesn't check, with every lookup, if the contents of /etc/resolv.conf have changed.
the solution is to add a call to res_init(), defined in resolv.h

* Update httplib.h

httplib.h

@@ -156,6 +156,9 @@ using socket_t = SOCKET;
 #include <ifaddrs.h>
 #include <netdb.h>
 #include <netinet/in.h>
+#ifdef __linux__
+#include <resolv.h>
+#endif
 #include <netinet/tcp.h>
 #ifdef CPPHTTPLIB_USE_POLL
 #include <poll.h>
@@ -1821,6 +1824,9 @@ socket_t create_socket(const char *host, int port, int socket_flags,
   auto service = std::to_string(port);
 
   if (getaddrinfo(host, service.c_str(), &hints, &result)) {
+#ifdef __linux__
+    res_init();
+#endif
     return INVALID_SOCKET;
   }