a more stupid way of doing middle chaining, but at least it is clearer.

block.go

@@ -8,7 +8,7 @@ import (
 	"time"
 )
 
-func agentBlock(next http.Handler) http.Handler {
+func agentBlock(next http.HandlerFunc) http.HandlerFunc {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		ua := r.Header.Get("User-Agent")
 		for _, bua := range []string{"Amazonbot", "semrush", "Bytespider", "AhrefsBot"} {
@@ -22,7 +22,7 @@ func agentBlock(next http.Handler) http.Handler {
 	})
 }
 
-func cloudflareBlock(next http.Handler) http.Handler {
+func cloudflareBlock(next http.HandlerFunc) http.HandlerFunc {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		ip := net.ParseIP(actualIP(r))
 		if ip != nil {

http_middleware.go

@@ -2,7 +2,7 @@ package main
 
 import "net/http"
 
-func loggingMiddleware(next http.Handler) http.Handler {
+func loggingMiddleware(next http.HandlerFunc) http.HandlerFunc {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		path := r.URL.Path
 		if r.URL.RawQuery != "" {

main.go

@@ -144,15 +144,21 @@ func main() {
 	mux.HandleFunc("/{code}", renderEvent)
 	mux.HandleFunc("/{$}", renderHomepage)
 
-	var mainHandler http.Handler = relay
-	// apply http middlewares
-	for _, middleware := range []func(http.Handler) http.Handler{
-		cors.Default().Handler,
-		loggingMiddleware,
-		agentBlock,
-		cloudflareBlock,
-	} {
-		mainHandler = middleware(mainHandler)
+	corsH := cors.Default()
+	corsM := func(next http.HandlerFunc) http.HandlerFunc {
+		return corsH.Handler(next).ServeHTTP
+	}
+
+	var mainHandler http.HandlerFunc = func(w http.ResponseWriter, r *http.Request) {
+		cloudflareBlock(
+			agentBlock(
+				loggingMiddleware(
+					corsM(
+						relay.ServeHTTP,
+					),
+				),
+			),
+		)(w, r)
 	}
 
 	log.Print("listening at http://0.0.0.0:" + s.Port)