```rust
use appwrite::Client;
use appwrite::services::Locale;
#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
let client = Client::new();
client.set_endpoint("https://<REGION>.cloud.appwrite.io/v1"); // Your API Endpoint
client.set_project("<YOUR_PROJECT_ID>"); // Your project ID
client.set_session(""); // The user session to authenticate with
let locale = Locale::new(&client);
let result = locale.list_countries().await?;
let _ = result;
Ok(())
}
```