Example Nginx (built with OpenResty’s Lua module) config adding a header with the time since epoch to responses

nginx.conf

events {
  worker_connections 42;
}

http {
  server {
    listen 8080;

    header_filter_by_lua_block {
      ngx.header['X-Epoch'] = ngx.time()
    }

    location / {
      return 200 'Hello, World!';
    }
  }
}