chore(examples): Add Cors to grpc web server (#1320)

examples/src/grpc-web/server.rs

@@ -3,6 +3,7 @@ use tonic::{transport::Server, Request, Response, Status};
 use hello_world::greeter_server::{Greeter, GreeterServer};
 use hello_world::{HelloReply, HelloRequest};
 use tonic_web::GrpcWebLayer;
+use tower_http::cors::CorsLayer;
 
 pub mod hello_world {
     tonic::include_proto!("helloworld");
@@ -38,7 +39,13 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     println!("GreeterServer listening on {}", addr);
 
     Server::builder()
+        // GrpcWeb is over http1 so we must enable it.
         .accept_http1(true)
+        // Use the Cors layer from `tower-http`.
+        .layer(CorsLayer::new())
+        // Apply the tonic-web layer to convert
+        // http1 requests into something that
+        // the core tonic code can understand.
         .layer(GrpcWebLayer::new())
         .add_service(greeter)
         .serve(addr)