with_concurrency_with_order.go

package main

import (
	"fmt"
	"sync"
	"time"
)

var wg sync.WaitGroup

func main() {
	start := time.Now()

	wg.Add(4)

	firstchan := make(chan string)
	secondchan := make(chan string)
	thirdchan := make(chan string)
	fourthchan := make(chan string)

	go FourthFunc(fourthchan)
	go SecondFunc(secondchan)
	go FirstFunc(firstchan)
	go ThirdFunc(thirdchan)

	fmt.Println(<-firstchan)
	fmt.Println(<-secondchan)
	fmt.Println(<-thirdchan)
	fmt.Println(<-fourthchan)

	wg.Wait()

	fmt.Printf("Total time to finish : %s \n", time.Since(start).String())

}

func FirstFunc(ch chan<- string) {
	fmt.Println("-- Executing first function --")
	time.Sleep(7 * time.Second)
	defer wg.Done()

	ch <- "-- First Function finished --"
}

func SecondFunc(ch chan<- string) {
	fmt.Println("-- Executing second function --")
	time.Sleep(5 * time.Second)
	defer wg.Done()

	ch <- "-- Second Function finished --"
}

func ThirdFunc(ch chan<- string) {
	fmt.Println("-- Executing third function --")
	time.Sleep(2 * time.Second)
	defer wg.Done()

	ch <- "-- Third Function finished --"
}

func FourthFunc(ch chan<- string) {
	fmt.Println("-- Executing fourth function --")
	time.Sleep(10 * time.Second)
	defer wg.Done()

	ch <- "-- Fourth Function finished --"
}