How to Convert Between Sync and Async Code in Rust

Use the async keyword to define a function that returns a Future and the .await keyword to pause execution until that future completes.

use trpl::Html;

async fn page_title(url: &str) -> Option<String> {
    let response_text = trpl::get(url).await.text().await;
    Html::parse(&response_text)
        .select_first("title")
        .map(|title| title.inner_html())
}

To run this async code from a synchronous main function, you must use an async runtime like tokio to spawn the task and await its result.

Async code lets your program start a long task, like downloading a file, and do other work while waiting for it to finish. Instead of blocking the entire program, it pauses the specific task and resumes it automatically when the data arrives. Think of it like ordering food at a restaurant: you place your order and can chat with friends while the kitchen cooks, rather than standing at the counter staring at the stove.