rocket_cors | origin resource sharing for Rocket.rs applications | REST library

I'm trying to add a CORS policy to my rocket API. I've tried a couple ways but the closest (I think) and most straightforward way so far has been to add a custom Fairing that sets the CORS headers in the on_response hook. I've been using the Fairings implementation guide and this answer to a similar question, but I am running into complaints about lifetimes.

This is the on_response hook.

I have a rocket (0.5.0-rc.1) route, that returns a content::Json and I would like to add CORS to that route using rocket_cors (from master).

Specifically I want to use the RequestGuard, because I only want to enable CORS for certain routes.

My original request looked like this:

I create a REST API with Rust and Rocket that works with swagger. Now I'm trying to consumes this API with React react-admin to be precise. Everything works OK until I need to call a list where the famous X-Total-Count problem appears, and I am not able to solve it, probably due to lack of experience with Rust.

This is the message "The X-Total-Count header is missing in the HTTP Response. The jsonServer Data Provider expects responses for lists of resources to contain this header with the total number of results to build the pagination. If you are using CORS, did you declare X-Total-Count in the Access-Control-Expose-Headers header"

This is my response header

I'm new to rust and I'm using rocket to create a simple CRUD API that I later would like to put on an AWS EC2 bucket. I've got one or two basic routes and I wanted to start to implement CORS so a react app can call my API. I've tried multiple tutorials and example but I'm still stuck.

Tutorials I've looked at:

• https://www.steadylearner.com/blog/read/How-to-use-CORS-and-OPTIONS-HTTP-request-with-Rust-Rocket
• https://docs.rs/rocket/0.3.6/rocket/fairing/trait.Fairing.html

I've got a backend running rocket.rs which my flutter web app sends a request to, but it can't get past the OPTIONS response.

I have tried adding CORS (rocket_cors) to the backend and having a options response, but it still sends back:

I'm writing a simple web with Rocket as backend and React as frontend.

The code snippet looks like this for login page

I'm kinda new to the concept of how Rust works even after experimenting with it for a couple months. I'm writing a webserver with R2D2 (0.8.0) and Rocket (0.4.4) + Rocket_cors (0.5.2)

Rocket allows you to feed it structs into a state pool, so I don't have to initialize my Postgres server every time somebody sends a request. Here's the code: