golang: memory increases when server does not read requests' body

http-client.go

package main

import (
	"fmt"
	"io/ioutil"
	"net/http"
	"runtime"
	"strings"
	"time"
)

var serverURL = "http://localhost:4040"

func main() {
	monitorRuntime()

	for {
		sendHTTPRequest(buildHTTPRequest(), getHTTPClient())
		time.Sleep(10 * time.Millisecond)
	}
}

func buildHTTPRequest() (*http.Request) {
	data := strings.Repeat("x", 1048576) // 1048576 -> 1MB

	req, err := http.NewRequest(http.MethodPost, serverURL, strings.NewReader(data))
	if err != nil {
		panic(fmt.Sprintf("failed to build HTTP request: %v", err))
	}

	req.Close = true

	return req
}

func sendHTTPRequest(req *http.Request, cli *http.Client) {
	resp, err := cli.Do(req)
	if err != nil {
		// write tcp [::1]:54091->[::1]:4040: write: protocol wrong type for socket
		// write tcp [::1]:54096->[::1]:4040: write: broken pipe
		return
	}

	defer resp.Body.Close()
	_, _ = ioutil.ReadAll(resp.Body)
}

func getHTTPClient() *http.Client {
	c := http.DefaultClient

	return c
}

func monitorRuntime() {
	go func() {
		for {
			var m runtime.MemStats
			runtime.ReadMemStats(&m)

			fmt.Println(
				fmt.Sprintf(
					"memo-sys-mb: %5v \t\t heap-inuse-mb: %5v \t\t heap-objects: %5v",
					bToMb(m.Sys),
					bToMb(m.HeapInuse),
					m.HeapObjects,
				),
			)

			time.Sleep(5 * time.Second)
		}
	}()
}

func bToMb(b uint64) uint64 {
	return b / 1024 / 1024
}

http-server.go

package main

import (
	"fmt"
	"log"
	"net/http"
)

func handler(w http.ResponseWriter, r *http.Request) {
	w.WriteHeader(http.StatusOK)
	fmt.Fprintf(w, "{\"jsonrpc\": \"2.0\", \"error\": {\"code\": -32000, \"message\": \"Something went wrong...\"}, \"id\": \"1\"}")
}

func main() {
	http.HandleFunc("/", handler)
	log.Fatal(http.ListenAndServe(":4040", nil))
}