Add pathvalue example to README and implement PathValue handler. (#985)

Author: catatsuy

_examples/README.md

@@ -12,6 +12,7 @@ chi examples
 * [router-walk](https://github.com/go-chi/chi/blob/master/_examples/router-walk/main.go) - Print to stdout a router's routes
 * [todos-resource](https://github.com/go-chi/chi/blob/master/_examples/todos-resource/main.go) - Struct routers/handlers, an example of another code layout style
 * [versions](https://github.com/go-chi/chi/blob/master/_examples/versions/main.go) - Demo of `chi/render` subpkg
+* [pathvalue](https://github.com/go-chi/chi/blob/master/_examples/pathvalue/main.go) - Demonstrates `PathValue` usage for retrieving URL parameters
 
 
 ## Usage

_examples/pathvalue/main.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/go-chi/chi/v5"
+)
+
+func main() {
+	r := chi.NewRouter()
+
+	// Registering a handler that retrieves a path parameter using PathValue
+	r.Get("/users/{userID}", pathValueHandler)
+
+	http.ListenAndServe(":3333", r)
+}
+
+// pathValueHandler retrieves a URL parameter using PathValue and writes it to the response.
+func pathValueHandler(w http.ResponseWriter, r *http.Request) {
+	userID := r.PathValue("userID")
+
+	// Respond with the extracted userID
+	w.Write([]byte(fmt.Sprintf("User ID: %s", userID)))
+}