ADD: axum middleware example (#785)

Author: wduminy

examples/http-axum-middleware/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "http-axum-middleware"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+axum = "0.7"
+lambda_http = { path = "../../lambda-http", default-features = false, features = [
+  "apigw_rest",
+] }
+lambda_runtime = { path = "../../lambda-runtime" }
+serde_json = "1.0"
+tokio = { version = "1", features = ["macros"] }
+tracing = { version = "0.1", features = ["log"] }
+tracing-subscriber = { version = "0.3", default-features = false, features = [
+  "fmt",
+] }
+

examples/http-axum-middleware/README.md

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+# AWS Lambda Function example
+
+## Build & Deploy
+
+1. Install [cargo-lambda](https://github.com/cargo-lambda/cargo-lambda#installation)
+2. Build the function with `cargo lambda build --release`
+3. Deploy the function to AWS Lambda with `cargo lambda deploy --iam-role YOUR_ROLE`
+
+## Build for ARM 64
+
+Build the function with `cargo lambda build --release --arm64`

examples/http-axum-middleware/src/main.rs

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+//! This example demonstrates how [axum middleware](https://docs.rs/axum/latest/axum/middleware/index.html)
+//! can be implemented.
+//!
+//! To test this:
+//! ```sh
+//! # start the local server
+//! cargo lambda watch
+//! # Then send through an example request
+//! cargo lambda invoke --data-example apigw-request
+//! ```
+
+use axum::{response::Json, routing::post, Router};
+use lambda_http::request::RequestContext::ApiGatewayV1;
+use lambda_http::{run, Error};
+use serde_json::{json, Value};
+
+// Sample middleware that logs the request id
+async fn mw_sample(req: axum::extract::Request, next: axum::middleware::Next) -> impl axum::response::IntoResponse {
+    let context = req.extensions().get::<lambda_http::request::RequestContext>();
+    if let Some(ApiGatewayV1(ctx)) = context {
+        tracing::info!("RequestId = {:?}", ctx.request_id);
+    }
+    next.run(req).await
+}
+
+async fn handler_sample(body: Json<Value>) -> Json<Value> {
+    Json(json!({ "echo":  *body }))
+}
+
+#[tokio::main]
+async fn main() -> Result<(), Error> {
+    tracing_subscriber::fmt()
+        .with_max_level(tracing::Level::INFO)
+        .with_target(false)
+        .without_time()
+        .init();
+
+    let app = Router::new()
+        .route("/testStage/hello/world", post(handler_sample))
+        .route_layer(axum::middleware::from_fn(mw_sample));
+
+    run(app).await
+}