limit max request size example

main.go

package main

import (
	"io"
	"net/http"
)

const maxLen = 10

func handler(w http.ResponseWriter, r *http.Request) {
	body, err := io.ReadAll(io.LimitReader(r.Body, maxLen+1))
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		return
	}
	defer r.Body.Close()
	if len(body) > maxLen {
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	io.WriteString(w, "OK")
}

func main() {
	http.HandleFunc("/", handler)
	http.ListenAndServe("localhost:8080", nil)
}