JupyterLab config to log in by custom language

Hi~ I want to know how to set the default language so that jupyter can automatically switch to my configured default language when logging in?
I’ve use a JupyterLab docker to login JupyterLab Web UI. I’ve found JupyterLab use English by default language. I’ve also install jupyterlab-language-pack-zh-CN in my docker.
But What I want is that users can use the language I installed when logging in for the first time, instead of manually switching every time. I’ve search some issues, but I can not found how to set. Can anybody help me?