How-To-Implement-Concurrency-With-Goroutines-and-Channels

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I wish I could be more like you.

Sequential Async Call

Let’s start with a basic console program that connects to a few website urls and tests if the connection is successful. There are no goroutines at start, and all calls are made in order which is not very efficient.

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package main

import "fmt"
import "net/http"
import "time"

func main() {
  start := time.Now()
  links := []string {
    "https://go.dev/learn/",
    "https://www.netflix.com/",
    "https://go.dev/learn/",
    "https://www.netflix.com/",
    "https://go.dev/learn/",
    "https://www.netflix.com/",
    "https://github.com/",
  }
  
  checkUrls(links)
  fmt.Println("Completed the code process, took: %f seconds", time.Since(start).Seconds())
}

func checkUrls(urls []string) {
  for _, link := range urls {
    checkUrl(link)
  }
}
func checkUrl(url string) {
  _, err := http.Get(url)
  
  if err != nil {
    fmt.Println("We could not reach: ", url)
  } else {
    fmt.Println("Success reaching the website: ", url)
  }
}

Adding Concurrency and Optimizing the code

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package main

import "fmt"
import "sync"
import "net/http"
import "time"

func main() {
  start := time.Now()
  links := []string {
    "https://go.dev/learn/",
    "https://www.netflix.com/",
    "https://go.dev/learn/",
    "https://www.netflix.com/",
    "https://go.dev/learn/",
    "https://www.netflix.com/",
    "https://github.com/",
  }
  
  checkUrls(links)
  fmt.Println("Completed the code process, took: %f seconds", time.Since(start).Seconds())
}

func checkUrls(urls []string) {
  c := make(chan string)
  var wg sync.WaitGroup
  
  for _, link := range urls {
    wg.Add(1)
    go checkUrl(link, c, &wg)
  }
  
  go func() {
    wg.Wait()
    close(c)
  }()
  
  for msg := range c {
    fmt.Println(msg)
  }
}


func checkUrl(url string, c chan string, wg *sync.WaitGroup) {
  defer (*wg).Done()
  _, err := http.Get(url)
  
  if err != nil {
    c <- "We could not reach: " + url
  } else {
    c <- "Success reaching the website: " + url
  }
}

https://faun.pub/golang-tutorial-how-to-implement-concurrency-with-goroutines-and-channels-67d0f30d9e35