Access a variable from another function in rust

Question

Hello I have a variable with a string here:

#[post("/select_date", data = "<time>")]
fn select_date(time: Form<SelectDate>) -> Result<Redirect, Error>{
    println!("{:#?}", time.date);
    let f_time = &time.date;
    Ok(Redirect::to("/"))
}

and I need to have the variable readable from here in the same file

#[get("/")]
async fn index(user: Option<User>) -> Template {
    let f_time = "";//here i would like to have that string
    Template::render("index", json!({ "user": user, "f_time ": f_time }))
}

I can't return the string in the select_date function because it needs to return the redirect to the index page otherwise it would be a black page.