examples: fix missing header

stephanlachnit · stephanlachnit · commit 3f8cc0ae992e · 2022-08-12T13:36:12.000+02:00
Signed-off-by: Stephan Lachnit &lt;stephanlachnit@debian.org&gt;
diff --git a/examples/pubsub_multithread_inproc.cpp b/examples/pubsub_multithread_inproc.cpp
@@ -1,6 +1,7 @@
 #include <future>
 #include <iostream>
 #include <string>
+#include <thread>
 
 #include "zmq.hpp"
 #include "zmq_addon.hpp"
