How to set up web server to perform POST Request in Go?

I want to set up a web server to perform a POST request. How does the post request get executed with the code below since only HandleFunc and ListenAndServe are defined in main function?

package main

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

func post(w http.ResponseWriter, r *http.Request) {
  const myurl string = "http://localhost:8000/"
  request := strings.NewReader(`
  {
	"Name":"Tom",
	"Age":"20" 
  }
`)
  response, err := http.Post(myurl, "application/json", request)
  content, err := ioutil.ReadAll(response.Body)
  if err != nil {
	 panic(err)
  }
  fmt.Println(string(content))
  defer response.Body.Close()
  }
func main() {
  http.HandleFunc("/", post)
  log.Fatal(http.ListenAndServe(":8000", nil))
}

Here is a basic example of how you could go about it. I am using the same program to run both, the server and the client. This is just for demonstration purposes. You can of course make them separate programs.

// use struct to represent the data 
// to recieve and send
type Person struct {
	Name string `json:"name"`
	Age  int    `json:"age"`
}

// run the example
func main() {
	// start the server in a goroutine
	go server()

	// wait 1 second to give the server time to start
	time.Sleep(time.Second)

	// make a post request
	if err := client(); err != nil {
		fmt.Println(err)
	}
}

// basic web server to receive a request and 
// decode the body into a user struct
func server() {
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost  {
			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
			return
		}

		user := &Person{}
		err := json.NewDecoder(r.Body).Decode(user)
		if err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}

		fmt.Println("got user:", user)
		w.WriteHeader(http.StatusCreated)
	})

	if err := http.ListenAndServe(":8080", nil); err != http.ErrServerClosed {
		panic(err)
	}
}

// a simple client that posts a user to the server
func client() error {
	user := &Person{
		Name: "John",
		Age:  30,
	}

	b := new(bytes.Buffer)
	err := json.NewEncoder(b).Encode(user)
	if err != nil {
		return err
	}

	resp, err := http.Post("http://localhost:8080/", "application/json", b)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	fmt.Println(resp.Status)
	return nil
}

Here is the working example: https://go.dev/play/p/34GT04jy_uA