Bind Fails with `Transfer-Encoding: chunked`

[178inaba]

Issue Description

Bind fails when Transfer-Encoding: chunked is used.

Working code to debug

Server

package main

import (
	"fmt"
	"net/http"
	"net/http/httputil"

	"github.com/labstack/echo/v4"
)

type User struct {
	Name  string `json:"name"`
	Email string `json:"email"`
}

func main() {
	e := echo.New()
	e.POST("/", func(c echo.Context) error {
		req := c.Request()

		fmt.Println("----------")
		fmt.Println("ContentLength:", req.ContentLength)
		fmt.Println("TransferEncoding:", req.TransferEncoding)
		fmt.Println("----------")

		reqDump, err := httputil.DumpRequest(req, true)
		if err != nil {
			return err
		}
		fmt.Println(string(reqDump))

		var u User
		if err := c.Bind(&u); err != nil {
			return err
		}

		return c.JSON(http.StatusOK, u)
	})

	e.Logger.Fatal(e.Start(":1323"))
}

Log

----------
ContentLength: -1
TransferEncoding: [chunked]
----------
POST / HTTP/1.1
Host: localhost:1323
Transfer-Encoding: chunked
Accept-Encoding: gzip
Content-Type: application/json
User-Agent: Go-http-client/1.1

28
{"name":"foo","email":"foo@example.com"}
0

Client

package main

import (
	"bytes"
	"fmt"
	"io"
	"log"
	"net/http"
	"net/http/httputil"
)

func main() {
	req, err := http.NewRequest("POST", "http://localhost:1323", bytes.NewBufferString(`{"name":"foo","email":"foo@example.com"}`))
	if err != nil {
		log.Fatal(err)
	}
	req.Header.Set("Content-Type", "application/json")
	req.ContentLength = 0

	reqDump, err := httputil.DumpRequest(req, true)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(string(reqDump))

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		log.Fatal(err)
	}
	defer resp.Body.Close()

	b, err := io.ReadAll(resp.Body)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Println("----------")
	fmt.Println(string(b))
}

Log

POST / HTTP/1.1
Host: localhost:1323
Content-Type: application/json

{"name":"foo","email":"foo@example.com"}
----------
{"name":"","email":""}

Version/commit

v4.13.0