Go parallel execution

main.go

package main

import (
	"errors"
	"log"
	"time"
	"sync"
	"fmt"
)

func ping(wg *sync.WaitGroup, fatalErrors chan error, url string) {
	defer wg.Done()

	fmt.Printf("ping %v: Started\n", url)
	time.Sleep(time.Second)

	if url == "err" {
		fatalErrors <- errors.New(fmt.Sprintf("Error in host %s", url))
	}

	fmt.Printf("ping %v: Finished\n", url)
}

func main() {

	start := time.Now()

	urls := [4]string{"https://google.com", "https://cisco.com", "https://amazon.com", "err"}

	// Make channels to pass fatal errors in WaitGroup
	fatalErrors := make(chan error)
	wgDone := make(chan bool)

	var wg sync.WaitGroup
	for _, url := range urls {
		wg.Add(1)
		go ping(&wg, fatalErrors, url)
	}

	// Important final goroutine to wait until WaitGroup is done
	go func() {
		wg.Wait()
		close(wgDone)
	}()

	// Wait until either WaitGroup is done or an error is received through the channel
	select {
		case <-wgDone:
			break
		case err := <-fatalErrors:
			elapsed := time.Since(start)
			close(fatalErrors)
			log.Fatal(fmt.Sprintf("Error caught, time: %s", elapsed), err)
	}

	elapsed := time.Since(start)
	log.Println(fmt.Sprintf("Success, time: %s", elapsed))
}

output.log

$  go run .
Worker https://cisco.com: Started
Worker https://amazon.com: Started
Worker https://google.com: Started
Worker err: Started
Worker err: Finished
Worker https://amazon.com: Finished
Worker https://google.com: Finished
Worker https://cisco.com: Finished
2021/11/05 18:05:02 Error caught, time: 1.000449656s Error in host err
exit status 1