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Catch values from Goroutines

The most natural way to fetch a value from a goroutine is channels. Channels are the pipes that connect concurrent goroutines. You can send values into channels from one goroutine and receive those values into another goroutine or in a synchronous function.

Example

package main

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

// WaitGroup is used to wait for the program to finish goroutines.
var wg sync.WaitGroup

func responseSize(url string, nums chan int) {
	// Schedule the call to WaitGroup's Done to tell goroutine is completed.
	defer wg.Done()

	response, err := http.Get(url)
	if err != nil {
		log.Fatal(err)
	}
	defer response.Body.Close()
	body, err := ioutil.ReadAll(response.Body)
	if err != nil {
		log.Fatal(err)
	}
	// Send value to the unbuffered channel
	nums <- len(body)
}

func main() {
	nums := make(chan int) // Declare a unbuffered channel
	wg.Add(1)
	go responseSize("https://www.golangprograms.com", nums)
	fmt.Println(<-nums) // Read the value from unbuffered channel
	wg.Wait()
	close(nums) // Closes the channel
}

Output

79655
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