A simple Cloudflare Workers Rust HTTP Router Sample from Official Example: https://github.com/cloudflare/workers-rs/tree/main/examples/router

Cargo.toml

[package]
name = "router-on-workers"
version = "0.0.1"
edition = "2021"

[package.metadata.release]
release = false

[lib]
crate-type = ["cdylib"]

[dependencies]
serde = "1.0.188"
worker = { version="0.5.0", features=['http'] }
worker-macros = { version="0.5.0", features=['http'] }
console_error_panic_hook = { version = "0.1.1" }
http = "1.1"
serde_json = "1.0.140"

[dev-dependencies]
tokio = { version = "1", features = ["full"] }

lib.rs

// src/lib.rs
use serde::{Deserialize, Serialize};
use serde_json::Value;
use worker::*;

#[derive(Debug, Deserialize, Serialize)]
struct GenericResponse {
    status: u16,
    message: String,
}

#[event(fetch)]
async fn main(req: Request, env: Env, _ctx: Context) -> Result<Response> {
    Router::new().get_async("/", handle_get).run(req, env).await
}

pub async fn handle_get(req: Request, _ctx: RouteContext<()>) -> worker::Result<Response> {
    // ?id=1
    let url = req.url()?;
    let id = url
        .query_pairs()
        .find(|(key, _)| key == "id")
        .map(|(_, value)| value.to_string())
        .unwrap_or("1".to_string());

    // make json placeholder api
    let mut response =
        Fetch::Url(format!("https://jsonplaceholder.typicode.com/posts/{}", id).parse()?)
            .send()
            .await?;
    let body = response.text().await?;
    let json: Value = serde_json::from_str(&body)?;

    // install serde_json by using cargo add serde_json
    Response::from_json(&json)
}

package.json

{
	"name": "router-on-workers",
	"version": "0.0.1",
	"private": true,
	"scripts": {
		"deploy": "wrangler deploy",
		"dev": "wrangler dev --local"
	},
	"devDependencies": {
		"wrangler": "^3"
	}
}

wrangler.toml

name = "router-on-workers"
main = "build/worker/shim.mjs"
compatibility_date = "2023-03-22"

[build]
command = "cargo install worker-build && worker-build --release"