docs: Add more examples

Signed-off-by: Xuanwo <github@xuanwo.io>

src/lib.rs

@@ -68,6 +68,92 @@
 //!     Ok(())
 //! }
 //! ```
+//!
+//! Retry functions with args.
+//!
+//! ```no_run
+//! use anyhow::Result;
+//! use backon::ExponentialBuilder;
+//! use backon::Retryable;
+//!
+//! async fn fetch(url: &str) -> Result<String> {
+//!     Ok(reqwest::get(url).await?.text().await?)
+//! }
+//!
+//! #[tokio::main(flavor = "current_thread")]
+//! async fn main() -> Result<()> {
+//!     let content = (|| async { fetch("https://www.rust-lang.org").await })
+//!         .retry(&ExponentialBuilder::default())
+//!         .when(|e| e.to_string() == "retryable")
+//!         .await?;
+//!
+//!     println!("fetch succeeded: {}", content);
+//!     Ok(())
+//! }
+//! ```
+//!
+//! Retry functions with receiver `&self`.
+//!
+//! ```no_run
+//! use anyhow::Result;
+//! use backon::ExponentialBuilder;
+//! use backon::Retryable;
+//!
+//! struct Test;
+//!
+//! impl Test {
+//!     async fn fetch(&self, url: &str) -> Result<String> {
+//!         Ok(reqwest::get(url).await?.text().await?)
+//!     }
+//! }
+//!
+//! #[tokio::main(flavor = "current_thread")]
+//! async fn main() -> Result<()> {
+//!     let test = Test;
+//!     let content = (|| async { test.fetch("https://www.rust-lang.org").await })
+//!         .retry(&ExponentialBuilder::default())
+//!         .when(|e| e.to_string() == "retryable")
+//!         .await?;
+//!
+//!     println!("fetch succeeded: {}", content);
+//!     Ok(())
+//! }
+//! ```
+//!
+//! Retry functions with receiver `&mut self`.
+//!
+//! ```no_run
+//! use anyhow::Result;
+//! use backon::ExponentialBuilder;
+//! use backon::RetryableWithContext;
+//!
+//! struct Test;
+//!
+//! impl Test {
+//!     async fn fetch(&mut self, url: &str) -> Result<String> {
+//!         Ok(reqwest::get(url).await?.text().await?)
+//!     }
+//! }
+//!
+//! #[tokio::main(flavor = "current_thread")]
+//! async fn main() -> Result<()> {
+//!     let test = Test;
+//!
+//!     let (_, result) = (|mut v: Test| async {
+//!         let res = v.fetch("https://www.rust-lang.org").await;
+//!         // Return input context back.
+//!         (v, res)
+//!     })
+//!     .retry(&ExponentialBuilder::default())
+//!     // Passing context in.
+//!     .context(test)
+//!     .when(|e| e.to_string() == "retryable")
+//!     .await;
+//!
+//!     println!("fetch succeeded: {}", result.unwrap());
+//!     Ok(())
+//! }
+//! ```
 
 #![deny(missing_docs)]
 #![deny(unused_qualifications)]