Added example to README

README.md

@@ -20,6 +20,76 @@ This library is designed for direct communication with Google over HTTPS.
 It does not validate the id_token when converting it to a JWT,  
 so the id_token cannot be passed to other components of your app.
 [See document](https://developers.google.com/identity/openid-connect/openid-connect#obtainuserinfo)
+## Example
+Here's hou you can use this library with the axum framework.
+### 1. Create Config
+First, We create `Config` struct the is including Client ID, Secrets, etc...
+```rust
+let oidc_cfg = ConfigBuilder::new()
+    .auth_endpoint("https://accounts.google.com/o/oauth2/auth")
+    .client_id("my_client_id")
+    .client_secret("my_client_secret")
+    .token_endpoint("https://oauth2.googleapis.com/token")
+    .redirect_uri("http://localhost/auth/callback")
+    .build();
+```
+## 2. Login Handler
+Here's an example handler to start the login flow.
+```rust
+async fn login(
+    State(app_state): State<Arc<AppState>>,
+    jar: CookieJar,
+) -> Result<impl IntoResponse, AppError> {
+    // 1. generate redirect information for the OIDC authentication flow
+    let (csrf_token, _nonce, redirect_uri) = generate_auth_redirect(
+        &app_state.oidc_cfg,
+        AccessType::Online,
+        AdditionalScope::Both,
+    )
+    .map_err(WrapOIDCError)?;
+
+    // 2. Generate a key to store the csrf_token in Redis or memory,
+    //    and store it
+    // 3. Create and set a cookie
+    // ...(please implement these part as appropirate for your application)
+
+    // 4. Set the Cookie ant redirect to the authorization server
+    Ok((jar.add(cookie), Redirect::to(&redirect_uri)))
+}
+```
+### 3. Callback Handler
+Here’s an example of a callback handler for when the provider (like Google) redirects back.
+```rust
+async fn callback(
+    State(app_state): State<Arc<AppState>>,
+    jar: CookieJar,
+    req: Request,
+) -> Result<impl IntoResponse, AppError> {
+    // 1. Retrieve the csrf_token key from the cookie, then fetch the stored csrf_token
+
+    // 2. Verify the CSRF token & build the IDToken request
+    let id_token_req = create_id_token_request(&app_state.oidc_cfg, &csrf_token_val, req)
+        .map_err(WrapOIDCError)?;
+
+    // 3. Send request to Google
+    let id_token_res = send_id_token_req(&id_token_req)
+        .await
+        .map_err(WrapOIDCError)?;
+
+    // 4. Encode the IDToken from the raw string
+    let id_token = IDToken::from_id_token_raw(id_token_res.id_token()).map_err(WrapOIDCError)?;
+
+    // print id_token
+    println!("----IDToken----");
+    println!("{id_token:#?}");
+
+    Ok((StatusCode::OK, "login success"))
+}
+```
+
+Of course, you can use this library with other framework as well!
+
+See [example](examples/easy/id_token.rs) for more detailes.
 
 ## Contributing
 We are currently working on the official contribution guidelines.