Rust HN fetch example

Cargo.toml

[package]
name = "fetch_hn"
version = "0.1.0"
edition = "2018"

[dependencies]
serde = { version = "1.0.89", features = ["derive"] }
reqwest = "0.9.11"
crossbeam-utils = "0.6.5"

main.rs

use serde::Deserialize;
use std::sync::Mutex;

const STORIES_URL: &str = "https://hacker-news.firebaseio.com/v0/topstories.json";
const ITEM_URL_BASE: &str = "https://hacker-news.firebaseio.com/v0/item";

#[derive(Deserialize)]
struct Story {
    title: String,
}

fn main() {
    let story_ids: Vec<u64> = reqwest::get(STORIES_URL).unwrap().json().unwrap();
    // AtomicUsize would be simpler than Mutex here, but the point of this is
    // to give a Mutex example.
    let cursor = Mutex::new(0);
    crossbeam_utils::thread::scope(|s| {
        for _ in 0..8 {
            s.spawn(|_| loop {
                let index = {
                    let mut cursor_guard = cursor.lock().unwrap();
                    let index = *cursor_guard;
                    if index >= story_ids.len() {
                        return;
                    }
                    *cursor_guard += 1;
                    index
                };
                let story_url = format!("{}/{}.json", ITEM_URL_BASE, story_ids[index]);
                let story: Story = reqwest::get(&story_url).unwrap().json().unwrap();
                println!("{}", story.title);
            });
        }
    })
    .unwrap();
}