Go language context control function execution timeout return

use go Language implementation request url The content of , When it exceeds the specified time, it will automatically return

package main

import (
	"context"
	"errors"
	"fmt"
	"io"
	"net/http"
	"time"
)

func main() {
	content, err := getUrlContent("https://github.com/", 500*time.Millisecond)
	if err != nil {
		fmt.Println(err)
		return
	}
	fmt.Println(content)
}

// obtain url The content of , And set the timeout event 
func getUrlContent(url string, timeout time.Duration) (string, error) {
	type Resp struct {
		content string
		err     error
	}
	ctx, cancel := context.WithTimeout(context.Background(), timeout)// Timeout control context
	defer cancel()// When the function returns, call cancel, Avoid memory leaks 
	ch := make(chan Resp,1)// At the end of the subprocess, put the return value into the channel , Inform the current process that the sub process has ended 
	go func() {// Open the subprocess to get url Content 
		res, err := http.Get(url)
		if err != nil {
			ch <- Resp{"", err}
			return
		}
		defer res.Body.Close()
		body, err := io.ReadAll(res.Body)// Read the content 
		if err != nil {
			ch <- Resp{"", err}
			return
		}
		ch <- Resp{string(body), nil}
	}()
	// Current coordination process waiting , Listen for channel readable events 
	select {
	case resp := <-ch:// Sub process end event 
		return resp.content, resp.err
	case <-ctx.Done():// Timeout Events 
		return "", errors.New(" It's overtime ")
	}
}