Currently, I don't know of a way to write a short script for gopherjs serve that accesses the body, because the script can execute before the body is available.

It might be because I can't think of a way to do it, or because the default HTML served by gopherjs serve is not ideal.

We should find a good way. I'd like to be able to show beginners how easy it is to get started with gopherjs serve and writing a short script, and not have to get into the subtle details of order execution until more advanced lessons.

I tried to resolve this via #570, where I wrote:

it might still be better for gopherjs serve to optimize for beginners and short snippets, rather than performance and advanced features (like avoiding a flash of empty body).