Add rest and grpc example (#967)

* Add rest and grpc example

* remove needless dependencies

* Apply suggestions from code review

Co-authored-by: David Pedersen <[email protected]>

* Update examples/rest-grpc-multiplex/src/main.rs

Co-authored-by: David Pedersen <[email protected]>

* Update examples/rest-grpc-multiplex/src/main.rs

Co-authored-by: David Pedersen <[email protected]>

* Update examples/rest-grpc-multiplex/src/multiplex_service.rs

Co-authored-by: David Pedersen <[email protected]>

* Update examples/rest-grpc-multiplex/Cargo.toml

Co-authored-by: David Pedersen <[email protected]>

* Update examples/rest-grpc-multiplex/src/multiplex_service.rs

Co-authored-by: David Pedersen <[email protected]>

* clean noisy code

* fix nitpicks

* missing newline

Co-authored-by: David Pedersen <[email protected]>

examples/rest-grpc-multiplex/src/main.rs

@@ -0,0 +1,72 @@
+//! Run with
+//!
+//! ```not_rust
+//! cd examples && cargo run -p example-rest-grpc-multiplex
+//! ```
+
+use self::multiplex_service::MultiplexService;
+use axum::{routing::get, Router};
+use proto::{
+    greeter_server::{Greeter, GreeterServer},
+    HelloReply, HelloRequest,
+};
+use std::net::SocketAddr;
+use tonic::{Response as TonicResponse, Status};
+use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
+
+mod multiplex_service;
+
+mod proto {
+    tonic::include_proto!("helloworld");
+}
+
+#[derive(Default)]
+struct GrpcServiceImpl {}
+
+#[tonic::async_trait]
+impl Greeter for GrpcServiceImpl {
+    async fn say_hello(
+        &self,
+        request: tonic::Request<HelloRequest>,
+    ) -> Result<TonicResponse<HelloReply>, Status> {
+        tracing::info!("Got a request from {:?}", request.remote_addr());
+
+        let reply = HelloReply {
+            message: format!("Hello {}!", request.into_inner().name),
+        };
+
+        Ok(TonicResponse::new(reply))
+    }
+}
+
+async fn web_root() -> &'static str {
+    "Hello, World!"
+}
+
+#[tokio::main]
+async fn main() {
+    // initialize tracing
+    tracing_subscriber::registry()
+        .with(tracing_subscriber::EnvFilter::new(
+            std::env::var("RUST_LOG")
+                .unwrap_or_else(|_| "example_rest_grpc_multiplex=debug".into()),
+        ))
+        .with(tracing_subscriber::fmt::layer())
+        .init();
+
+    // build the rest service
+    let rest = Router::new().route("/", get(web_root));
+
+    // build the grpc service
+    let grpc = GreeterServer::new(GrpcServiceImpl::default());
+
+    // combine them into one service
+    let service = MultiplexService::new(rest, grpc);
+
+    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
+    tracing::debug!("listening on {}", addr);
+    axum::Server::bind(&addr)
+        .serve(tower::make::Shared::new(service))
+        .await
+        .unwrap();
+}