Server crash while compiling

[sabond]

1st of all, thank you for this article, I've found it extremely helpful learning about sapper, svelte, and graphql. It seems to compile fine until I make additions to the _schema.js. I'm getting the following error:

"sapper-graphql-subscriptions_sapper_\dev\server\server.js:13131
subscribe: async function* asyncRandomNumbers() {
^
SyntaxError: Unexpected token * at createScript (vm.js:80:10)
...
Server crashed"

Any idea what might be causing that?
Thanks!