01-07-http-context-timeout.go

package main

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

/**
HTTP Request で Context のタイムアウトを利用する。
*/
func main() {
	const TimeOutSec = 2
	client := &http.Client{}
	endpoint := "http://example.com"
	//endpoint := "http://example.com:8999"
	req, _ := http.NewRequest(http.MethodGet, endpoint, nil)
	ctx, cancel := context.WithTimeout(context.Background(), TimeOutSec * time.Second)
	defer func() {
		fmt.Println("OK timeout")
		cancel()
	}()

	ch := make(chan struct{})

	go func() {
		defer fmt.Println("Exit go routine func")

		req = req.WithContext(ctx)
		resp, err := client.Do(req)
		if err != nil {
			fmt.Printf("Error: %s", err)
			ch <- struct{}{}
			return
		}
		io.Copy(os.Stdout, resp.Body)
		fmt.Println("Done go routine")
		time.Sleep(5 * time.Second)
		ch <- struct{}{}
	}()

	fmt.Println("waiting...")
	<-ch
	fmt.Println("All done")
}