[duped]

The traditional thing would be to have an init() function that is required to be called at the top of main() or before any other methods that need it. But I agree with your point.

[never_inline]

Now lets say its an async cache instead of singleton.

[duped]

Return the cached item if it exists else spawn a task to update it (doing nothing if the task has already been spawned), await the task and return the cached item.

[never_inline]

Thanks, that's a useful trick.