How to install extensions of coder server?

Here’s my Dockerfile:

FROM linuxserver/code-server:latest

# the rest of the file

As you can see, I’m using an image that has a coder server on it (VS Code inside the browser).

And it works just fine. When I run it, I can see VS Code via localhost:8443.

However, when I try to install extensions on it, I receive errors. It complains that it can’t get the extension and sometimes gives me 403 error, other times a gibberish.

How can I fix it?

Source: Dockerfile Questions