fix: example change to verify the parameterless function fix

[hanabi1224]

Currently, a parameterless function with return type in the rust trait fn demo_get_n() -> i32; does not compile, this PR tries make a fix.

error: expected expression, found `,`

[ihciah]

Thank you for the fix! Could you only keep the fix itself? If it is needed to add more functions for the demo services, it is welcomed to add in another PR.

[hanabi1224]

Thank you for the fix! Could you only keep the fix itself? If it is needed to add more functions for the demo services, it is welcomed to add in another PR.

@ihciah I've re-purposed this PR and moved the fix itself to #11
Please let me know if there's anything else