Cargo can't do nested workspaces.

examples/main-example/src/main.rs

@@ -0,0 +1,20 @@
+// <main-example>
+use actix_web::{web, App, HttpRequest, HttpResponse, HttpServer};
+
+fn greet(req: HttpRequest) -> HttpResponse {
+    let name = req.match_info().get("name").unwrap_or("World");
+    HttpResponse::Ok().body(format!("Hello {}!", &name))
+}
+
+fn main() {
+    HttpServer::new(|| {
+        App::new()
+            .service(web::resource("/").to(greet))
+            .service(web::resource("/{name}").to(greet))
+    })
+    .bind("127.0.0.1:8088")
+    .unwrap()
+    .run()
+    .unwrap();
+}
+// </main-example>