Golang ServeHTTP make proxy error EOF on POST request - go

Question

I’m working on proxy server with gin and ServeHTTP. 
Actually GET and OPTIONS request works well. But when I trying multiples POST request I get EOF error one in two request.
I’ve test to make repeat request without proxy service and its work well, so there is something not working in my code.
Edit :
I have test POST proxy with https://ptsv2.com/ and all request response return 200 status code.
// main.go
package main
import (
"fmt"
"../pkg/api"
)
func main() {
fmt.Println("Starting server")
api.InitServer()
}
// routes.go
package api
import (
"github.com/gin-gonic/gin"
)
const serviceUrl = "http://localhost:8732"
func InitServer() {
router := gin.Default()
defineRoutes(router)
router.Run()
}
func defineRoutes(router *gin.Engine) {
router.GET("/ping", Ping)
router.POST("/*any", Proxy(serviceUrl))
}
// controller.go
package api
import (
"bytes"
"fmt"
"io/ioutil"
"net/http"
"net/http/httputil"
"net/url"
"strconv"
"github.com/gin-gonic/gin"
)
type transport struct {
http.RoundTripper
}
func (t *transport) RoundTrip(req *http.Request) (resp *http.Response, err error) {
resp, err = t.RoundTripper.RoundTrip(req)
if err != nil {
// EOF ERROR HERE
return nil, err
}
b, err := ioutil.ReadAll(resp.Body)
if err != nil {
return nil, err
}
err = resp.Body.Close()
if err != nil {
return nil, err
}
b = bytes.Replace(b, []byte("server"), []byte("schmerver"), -1)
body := ioutil.NopCloser(bytes.NewReader(b))
response := resp
response.Body = body
response.ContentLength = int64(len(b))
response.Header.Set("Content-Length", strconv.Itoa(len(b)))
response.Header.Set("Access-Control-Allow-Origin", "*")
return response, nil
}
func Proxy(targetUrl string) gin.HandlerFunc {
fn := func(c *gin.Context) {
remote, err := url.Parse(targetUrl)
if err != nil {
panic(err)
}
proxy := httputil.NewSingleHostReverseProxy(remote)
proxy.Director = func(req *http.Request) {
req.Header = c.Request.Header
req.Host = remote.Host
req.URL.Scheme = remote.Scheme
req.URL.Host = remote.Host
req.Close = true // True / False same result
}
proxy.Transport = &transport{http.DefaultTransport}
proxy.ServeHTTP(c.Writer, c.Request)
}
return fn
}

Answer 1

conclusion
your code have no bug. it works. maybe your network setting is wrong.
explain
I download your code and test it with a local backend server. It works.
appendix
backend server code
package main
import (
"fmt"
"github.com/gin-gonic/gin"
)
func main() {
fmt.Println("Starting server")
router := gin.Default()
router.POST("/*any", func(c *gin.Context) {
c.JSON(200, gin.H{
"mes": "hello",
})
})
router.Run(":8888")
}