TypeError: Failed to fetch when calling fetch from the Javascript action

[GuiWang]

I am running a javascript action that attempts to do a GET request using fetch. I am using the exact example that shows up in documentation for that rule.

async function getPost(id) {
  return await fetch(`https://jsonplaceholder.typicode.com/posts/` + id)
    .then((res) => res.json());
}

[[POST]] = await getPost(1);

However, when I call this code it always fails with the message "TypeError: Failed to fetch". Does anyone know what I'm doing wrong?