01-11-chan-http-sample.go

package main

import (
	"net/http"
	"fmt"
	"time"
)

func main() {
	type Result struct {
		Error error
		Response *http.Response
	}
	checkStatus := func(done <-chan struct{}, urls ...string) <-chan Result {
		results := make(chan Result)
		go func() {
			defer close(results)

			var i int
			for _, url := range urls {
				var result Result
				resp, err := http.Get(url)
				result = Result{Error: err, Response: resp}
				select {
				case <-done:
					fmt.Printf("%d: got done channel.\n", i)
					return
				case results <- result:
					fmt.Printf("%d: got result.\n", i)
				}
				i++
			}
			fmt.Println("Completed go routine.")
		}()
		return results
	}

	done := make(chan struct{})
	defer close(done)

	defer func() {
		time.Sleep(3 * time.Second)
		fmt.Println("Done finally")
	}()

	errCounter := 0
	urls := []string{"a", "https://www.google.com", "https://badhost", "b", "c", "d"}
	//urls := []string{"a", "https://www.google.com", "https://www.yahoo.co.jp"}
	for result := range checkStatus(done, urls...) {
		if result.Error != nil {
			fmt.Printf("Error: %s\n", result.Error)
			errCounter += 1
			if errCounter >= 3 {
				fmt.Println("too many errors, breaking!")
				//close(done)
				break
			}
			continue
		}
		fmt.Printf("Reseponse: %v\n", result.Response.Status)
	}
	fmt.Println("done")

	time.Sleep(5 * time.Second)
}