debugging multiple threads with visual studio code

Question

I am setting some breakpoints in some async threaded code and I can't seem to figure out how to tell visual studio code to catch any threads in this code path.

fn main() {
  println!("hello world"); // hits this line when I set a breakpoint
  readTheFeed("https://www.coindesk.com/arc/outboundfeeds/rss/?outputType=xml");
}

async fn readTheFeed(feed_url: &str) -> Result<Channel, Box<dyn Error>> {
  let content = reqwest::get(feed_url) //doesn't hit any breakpoints in the async code
      .await?
      .bytes()
      .await?;
  let channel = Channel::read_from(&content[..])?;
  println!("{}", channel.title.to_string());
  println!("{}", channel.description.to_string());
  Ok(channel)
}

How do I tell visual studio code to break with any threads that hit this piece of code?

EDIT ----

I updated the code as aync task are "inert" meaning they don't run unless passed to an executer. Here's the updated code:

#[tokio::main]
async fn main() {
  let t = readTheFeed("https://www.coindesk.com/arc/outboundfeeds/rss/?outputType=xml");
  block_on(t);
}

async fn readTheFeed(feed_url: &str) -> Result<Channel, Box<dyn Error>> {
  let content = reqwest::get(feed_url)
      .await?
      .bytes()
      .await?;
  let channel = Channel::read_from(&content[..])?;
  println!("{}", channel.title.to_string());
  println!("{}", channel.description.to_string());
  Ok(channel)
}

Now I am getting the following error:

thread 'main' panicked at 'there is no reactor running, must be called from the context of a Tokio 1.x runtime', /Users/admin/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.17.0/src/runtime/context.rs:21:19

Answer 1

Try this:

#[tokio::main]
async fn main() {
  println!("hello world"); // hits this line when I set a breakpoint
  readTheFeed("https://www.coindesk.com/arc/outboundfeeds/rss/?outputType=xml").await;
}

async fn readTheFeed(feed_url: &str) -> Result<Channel, Box<dyn Error>> {
  let content = reqwest::get(feed_url) //doesn't hit any breakpoints in the async code
      .await?
      .bytes()
      .await?;
  let channel = Channel::read_from(&content[..])?;
  println!("{}", channel.title.to_string());
  println!("{}", channel.description.to_string());
  Ok(channel)
}

The problem is that this line:

readTheFeed("https://www.coindesk.com/arc/outboundfeeds/rss/?outputType=xml");

is just creating a future and immediately dropping it without running it. In order to run the future, you need an executor (which I provide with #[tokio::main], but there are other ways if you need more control) and then to await (or spawn) the future.