Content-Length header missing for empty POST requests

[N1cOs]

Hello! Recently we faced with a problem, that resty Client doesn't set Content-Length header for an empty POST request.

Version - 2.16.5.

Example:

package main

import (
	"fmt"

	"github.com/go-resty/resty/v2"
)

func main() {
	client := resty.New()

	client.OnBeforeRequest(func(client *resty.Client, request *resty.Request) error {
		request.
			SetBody(nil).
			SetContentLength(true)

		return nil
	})

	client = client.SetBaseURL("http://localhost:8080")

	resp, err := client.R().Execute("POST", "/test")
	if err != nil {
		panic(err)
	}

	fmt.Println(resp)
}

Then I captured request with Wireshark and Content-Length header is missing:

[N1cOs]

I did a little more research. It happens not only for POST requests but also for PUT, PATCH.

From version v2.16.2 there is a workaround to use http.NoBody explicitly.