Use request.Host over Host header

Go already figured out this

main.go

@@ -528,7 +528,7 @@ func getHost(r *http.Request) string {
 	}
 
 	// Fallback to Host header
-	if host := r.Header.Get("Host"); host != "" {
+	if host := r.Host; host != "" {
 		return host
 	}