diff --git a/guestbook-go/Dockerfile b/guestbook-go/Dockerfile
index bf25e7db..6d3c8eca 100644
--- a/guestbook-go/Dockerfile
+++ b/guestbook-go/Dockerfile
@@ -27,4 +27,4 @@ COPY ./public/index.html public/index.html
 COPY ./public/script.js public/script.js
 COPY ./public/style.css public/style.css
 CMD ["/app/main"]
-EXPOSE 3000
+EXPOSE 4000