build.rs

// build.rs
use std::env;
use std::fs;
use std::path::Path;

fn main() {
    let out_dir = env::var("OUT_DIR").unwrap();
    let dest_path = Path::new(&out_dir).join("routes.rs");
    let src_path = Path::new("src/pages");

    let mut routes = String::new();
    for entry in fs::read_dir(src_path).unwrap() {
        let entry = entry.unwrap();
        let path = entry.path();
        if path.is_file() {
            let file_name = path.file_stem().unwrap().to_str().unwrap();
            let route = format!("\"/{}\": \"{}\"", file_name, path.display());
            routes.push_str(&route);
            routes.push_str(",\n");
        }
    }

    let contents = format!("pub const ROUTES: &str = {{\n{}\n}};\n", routes);
    std::fs::write(dest_path, contents).unwrap();
    println!("cargo:rerun-if-changed=src/pages");
}

main.rs

include!(concat!(env!("OUT_DIR"), "/routes.rs"));

// use the routes in your code
for route in ROUTES.iter() {
    println!("{}", route);
}