Update docs with example usage

README.md

@@ -12,3 +12,39 @@ http log server
   -port int
         HTTP port (default 8080)
 ```
+
+Example Nginx config for mirroring requests:
+
+```nginx
+upstream backend {
+    server 127.0.0.1:8087;
+}
+
+upstream mirror_backend {
+    server 127.0.0.1:8080;
+}
+server {
+    listen       8086 default_server;
+    server_name  localhost;
+
+    # Send body to mirror.
+    mirror_request_body on;
+
+    # redirect server error pages to the static page /50x.html
+    #
+    error_page   500 502 503 504  /50x.html;
+    location = /50x.html {
+        root   /usr/share/nginx/html;
+    }
+
+    location / {
+        mirror @mirror;
+        proxy_pass http://backend;
+    }
+
+    location = @mirror {
+        internal;
+        proxy_pass http://mirror_backend$request_uri;
+    }
+}
+```