make api server use only a single thread

examples/server/CMakeLists.txt

@@ -2,6 +2,9 @@ set(TARGET server)
 include_directories(${CMAKE_CURRENT_SOURCE_DIR})
 add_executable(${TARGET} server.cpp json.hpp httplib.h)
 target_compile_definitions(${TARGET} PRIVATE
+    # single thread
+    CPPHTTPLIB_THREAD_POOL_COUNT=1
+    # crash the server in the debug mode, otherwise send http 500 error
     $<$<CONFIG:Debug>:
         CPPHTTPLIB_NO_EXCEPTIONS=1
     >