Concurrent Status Checker

package main

import (
	"fmt"
	"net/http"
	"net/http/httptest"
	"sort"
	"sync"
)

type Result struct {
	Path string
	Code int
}

func checkPaths(handler http.Handler, paths []string) []Result {
	results := make([]Result, 0, len(paths))
	resultCh := make(chan Result)
	var wg sync.WaitGroup

	for _, path := range paths {
		wg.Add(1)
		go func(path string) {
			defer wg.Done()
			request := httptest.NewRequest(http.MethodGet, path, nil)
			recorder := httptest.NewRecorder()
			handler.ServeHTTP(recorder, request)
			resultCh <- Result{Path: path, Code: recorder.Result().StatusCode}
		}(path)
	}

	go func() {
		wg.Wait()
		close(resultCh)
	}()

	for result := range resultCh {
		results = append(results, result)
	}
	sort.Slice(results, func(i, j int) bool {
		return results[i].Path < results[j].Path
	})
	return results
}

func main() {
	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		switch r.URL.Path {
		case "/", "/health":
			w.WriteHeader(http.StatusOK)
		default:
			http.NotFound(w, r)
		}
	})

	for _, result := range checkPaths(handler, []string{"/", "/missing", "/health"}) {
		fmt.Printf("%-8s %d\n", result.Path, result.Code)
	}
}