Hi Angela,
We are using **Node JS 10.x** in **GG 4.1**. Currently **GG 4.1** in our dev repo. you can find the installation instruction from dev repo here. https://github.com/GluuFederation/gluu-gateway/wiki/Installation-development-build
Also before **GG 4.1** installation, you need to uninstall your nodejs 8.
Best regards,
Meghna Joshi