Example of net/http Client not retrying or handling the case where the server closes the pooled connection before it knows and attempts to write the the pool conneciton.

readTimeoutExample.go

package main

import (
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"net"
	"net/http"
	"net/url"
	"time"
)

// Example of net/http client not attempting to reconnect to HTTP/1.1 reused
// connection if the server closed the connection due to read timeout.
//
// Seems to be a timing issue before net/http Client realizes the connection is
// closed, and a new request being made.
func main() {
	port := 8080
	// When server read timeout matches or within unknown range of request delay
	// the net/http Client will attempt to write to the connection but fail
	// because the server just then closed the connection. net/http Client will
	// not realize the error and retry the request.
	serverReadTimeout := 6 * time.Second
	requestDelay := 6 * time.Second

	go server(port, serverReadTimeout)
	time.Sleep(2 * time.Second)
	for {
		client(port)
		time.Sleep(requestDelay)
	}
}

func server(port int, readTimeout time.Duration) {
	listener, err := net.ListenTCP("tcp", &net.TCPAddr{Port: port})
	if err != nil {
		panic(err)
	}

	s := &http.Server{
		Handler:     serve,
		ReadTimeout: readTimeout,
	}
	if err := s.Serve(listener); err != nil {
		panic(err)
	}
}

var serve http.HandlerFunc = func(w http.ResponseWriter, r *http.Request) {
	if _, err := w.Write([]byte("hello there!")); err != nil {
		fmt.Println("server failed write:", err)
	}
}

func client(port int) {
	body := bytes.NewReader([]byte("hello everybody"))
	req, err := http.NewRequest("POST", fmt.Sprintf("http://localhost:%d", port), body)
	if err != nil {
		panic(err)
	}

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		if e, ok := err.(*url.Error); ok {
			if e.Err == io.EOF {
				// Do something with the failed request
				fmt.Println("Received io.EOF from request", e)
				return
			}
		}
		fmt.Println("client request err:", err)
		return
	}
	defer resp.Body.Close()

	b, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		fmt.Println("client read err:", err)
		return
	}

	fmt.Println("client response:", resp.StatusCode, string(b))
}