How to post a request to get cookie values and post new request by the previously obtained cookie By using Go language

here first post request is generating a variable cookie in the form [SID=pcmPXXx fidX1xxxX1cuK; Path=/; HttpOnly; SameSite=Strict]"

but i can't send this cookie to another post request (getting error).

sample go file with comments

package main

import (
  "fmt"
  "log"
  "strings"
  "net/http"
  "io/ioutil"
  "net/http/cookiejar"
)

var client http.Client
func init() {
    jar, err := cookiejar.New(nil)
    if err != nil {
        log.Fatalf("Got error while creating cookie jar %s", err.Error())
    }
    client = http.Client{
        Jar: jar,
    }
}

func main() {

  urlx := "http://localhost:8080/api/v2/auth/login"
  methodx := "POST"

  payloadx := strings.NewReader(`username=admin&password=strongadmin`)

  client := &http.Client {
  }
  reqx, err := http.NewRequest(methodx, urlx, payloadx)

  if err != nil {
    fmt.Println(err)
    return
  }
  reqx.Header.Add("Referer", "http://localhost:8080/")
  reqx.Header.Add("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/99.0.4844.51 Safari/537.36")
  reqx.Header.Add("Content-type", "application/x-www-form-urlencoded; charset=UTF-8")

  resx, err := client.Do(reqx)
  if err != nil {
    fmt.Println(err)
    return
  }
  defer resx.Body.Close()


  cookie := resx.Cookies()
  fmt.Println(cookie)

  bodyx, err := ioutil.ReadAll(resx.Body)
  if err != nil {
    fmt.Println(err)
    return
  }
  fmt.Println(string(bodyx))






  //second request start here 
// this var cookies is a dummy cookie that i manually written,
// i need to replace the below variable 'cookies' to previously obtained variable 'cookie' without error





  cookies := &http.Cookie{
      Name: "SID",
      Value: "PW16gD0Ja0OqixXeqpQle1WC/OK19tj ",
      MaxAge: 300,
  }
  url := "http://localhost:8080/api/changes"
  method := "POST"

  payload := strings.NewReader(`json={