Add solution for Challenge 5 (#732)

Co-authored-by: go-interview-practice-bot[bot] <230190823+go-interview-practice-bot[bot]@users.noreply.github.com>

Author: Johrespi

challenge-5/submissions/Johrespi/solution-template.go

@@ -0,0 +1,62 @@
+package main
+
+import (
+"fmt"
+"net/http"
+)
+
+const validToken = "secret"
+
+// AuthMiddleware checks the "X-Auth-Token" header.
+// If it's "secret", call the next handler.
+// Otherwise, respond with 401 Unauthorized.
+func AuthMiddleware(next http.Handler) http.Handler {
+return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+// TODO: Implement the logic:
+// 1) Grab the "X-Auth-Token" header
+// 2) Compare against validToken
+// 3) If mismatch or missing, respond with 401
+// 4) Otherwise pass to next handler
+
+token := r.Header.Get("X-Auth-Token")
+if token != validToken {
+http.Error(w, "", 401)
+return
+}
+next.ServeHTTP(w, r)
+})
+}
+
+// helloHandler returns "Hello!" on GET /hello
+func helloHandler(w http.ResponseWriter, r *http.Request) {
+if r.Method != http.MethodGet {
+http.Error(w, "xd", 401)
+return
+}
+fmt.Fprint(w, "Hello!")
+}
+
+// secureHandler returns "You are authorized!" on GET /secure
+func secureHandler(w http.ResponseWriter, r *http.Request) {
+fmt.Fprint(w, "You are authorized!")
+}
+
+// SetupServer configures the HTTP routes with the authentication middleware.
+func SetupServer() http.Handler {
+mux := http.NewServeMux()
+
+// Public route: /hello (no auth required)
+mux.HandleFunc("/hello", helloHandler)
+
+// Secure route: /secure
+// Wrap with AuthMiddleware
+secureRoute := http.HandlerFunc(secureHandler)
+mux.Handle("/secure", AuthMiddleware(secureRoute))
+
+return mux
+}
+
+func main() {
+// Optional: you can run a real server for local testing
+// http.ListenAndServe(":8080", SetupServer())
+}