Channels

channels/Makefile

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+run:
+	@go run main.go

channels/go.mod

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+module channelsdemo
+
+go 1.21.6

channels/main.go

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+package main
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"sync"
+)
+
+var Urls = []string{
+	"https://www.index.hr",
+	"https://www.vecernji.hr",
+	"https://www.jutarnji.hr",
+	"https://www.jutarnji.hrxxx/",
+}
+
+func fetchUrl(url string) (*string, error) {
+	resp, err := http.Get(url)
+	if err != nil {
+		return nil, err
+	}
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	bodyStr := string(body)
+
+	return &bodyStr, nil
+}
+
+func main() {
+	var wg sync.WaitGroup
+	chMessages := make(chan string)
+	chDone := make(chan bool)
+
+	wg.Add(len(Urls))
+
+	for _, url := range Urls {
+		go func(url string) {
+			defer wg.Done()
+
+			chMessages <- fmt.Sprintf("Fetching %s...", url)
+			body, err := fetchUrl(url)
+			if err != nil {
+				chMessages <- fmt.Sprintf("Error fetching %s. Length: %v", url, err)
+			} else {
+				chMessages <- fmt.Sprintf("Done fetching %s. Length: %d", url, len(*body))
+			}
+		}(url)
+	}
+
+	go func() {
+		for msg := range chMessages {
+			fmt.Println(msg)
+		}
+		// signal that message reader is done
+		chDone <- true
+	}()
+
+	wg.Wait()
+
+	// close messages channel to stop reading from message stream
+	close(chMessages)
+
+	// wait for chMessages reader to get done
+	<-chDone
+}