docs(README): add Typed error section in Snippets

README.md

@@ -437,6 +437,59 @@ async fn create_user(
 }
 ```
 
+### Typed errors
+
+```rust,no_run
+use ohkami::{Response, IntoResponse};
+use ohkami::serde::Serialize;
+use ohkami::format::JSON;
+use ohkami::fang::Context;
+
+enum MyError {
+    Sqlx(sqlx::Error),
+}
+impl IntoResponse for MyError {
+    fn into_response(self) -> Response {
+        match self {
+            Self::Sqlx(e) => Response::InternalServerError(),
+        }
+    }
+}
+
+#[derive(Serialize)]
+struct User {
+    id: u32,
+    name: String,
+}
+
+async fn get_user(
+    id: u32,
+    Context(pool): Context<'_, sqlx::PgPool>,
+) -> Result<JSON<User>, MyError> {
+    let sql = r#"
+        SELECT name FROM users WHERE id = $1
+    "#;
+    let name = sqlx::query_scalar::<_, String>(sql)
+        .bind(id as i64)
+        .fetch_one(pool)
+        .await
+        .map_err(MyError::Sqlx)?;
+
+    Ok(JSON(User { id, name }))
+}
+```
+
+[thiserror](https://crates.io/crates/thiserror) will improve error conversion:
+
+```rust,ignore
+    let name = sqlx::query_salor_as::<_, String>(sql)
+        .bind(id)
+        .fetch_one(pool)
+        // .await
+        // .map_err(MyError::Sqlx)?;
+        .await?;
+```
+
 ### Static directory serving
 
 ```rust,no_run