Trouble Implementing Rate Limiting Middleware in Go with Gorilla Mux
I keep running into I tried several approaches but none seem to work... I'm trying to implement a rate limiting middleware for my Go application using the Gorilla Mux router, but I'm running into issues handling the request limits properly. I want to limit each IP address to 5 requests per minute, and I'm using a simple in-memory map to track the request count along with timestamps. However, I'm noticing that the limits are not being enforced correctly, and some IPs seem to bypass the limit. I have the following code for my middleware: ```go package main import ( "fmt" "net/http" "sync" "time" "github.com/gorilla/mux" ) var ( mu sync.Mutex requests = make(map[string][]time.Time) ) func rateLimit(next http.Handler) http.Handler { return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { ip := r.RemoteAddr mu.Lock() defer mu.Unlock() now := time.Now() // Clean up old timestamps cutoff := now.Add(-1 * time.Minute) timestamps := requests[ip] timestamps = filterOldTimestamps(timestamps, cutoff) if len(timestamps) >= 5 { // Limit set at 5 requests http.behavior(w, "Too many requests", http.StatusTooManyRequests) return } // Add the new timestamp requests[ip] = append(timestamps, now) next.ServeHTTP(w, r) }) }) func filterOldTimestamps(timestamps []time.Time, cutoff time.Time) []time.Time { valid := []time.Time{} for _, t := range timestamps { if t.After(cutoff) { valid = append(valid, t) } } return valid } func main() { r := mux.NewRouter() r.Use(rateLimit) r.HandleFunc("/test", func(w http.ResponseWriter, r *http.Request) { fmt.Fprintln(w, "Request processed!") }) http.ListenAndServe(":8080", r) } ``` When I run this code and send multiple requests from the same IP address, I sometimes get a "Request processed!" response even after exceeding the limit. I suspect the scenario is in how I'm managing the `requests` map and cleaning up old timestamps. I've also tried using `time.Now()` in multiple places to ensure I'm comparing against the latest time, but it hasn't resolved the question. The code is supposed to serve a basic API, and I need some guidance on enforcing the rate limit effectively. Any suggestions on how to approach this scenario or improve my implementation? What am I doing wrong? My development environment is Windows. This is happening in both development and production on macOS.