Channels Exercise in Golan

The code is for the Go-Channels project from the Udemy course Go: The Complete Deeloper's Guide

The application checks regularly, on a 5 seconds interval, the state of the websites listed in the links slice of strings.

To avoid a potential hang-up waiting for a page to respond when the application would loop throught the slice of strings, checking one webpage at a time, Goroutines are implemented.

Functionality

func main() Loops through the links slice of strings once, creating a goroutine that will handle the checkLink(link, c) function. In its call, the channel c is given as an input.

After this initial loop, a second loop will watch the channel c (indefinitely). When a value comes out of it (from the checkLink function called previously), the value is assigned to a link l. This link is then used in a function literal (equivalent to a lambda in C++ or Python). The function literal is used so that the main routine isn't blocked by the time.Sleep() function. The link l is passed as a value

    go func(link string) {
    [...]
    } (l)

so that it's copied to guarantee that the child routine is using the same value that l pointed to when the child routine was created, instead of whichever one l was pointing at in the main for-loop.

func checkLink(link string, c chan string)

For every call it checks the state for the webpage indicated by link and verifies that there is no error err returned. If there is (f. ex. the page is down) it prints "might be down!" and exits the function.

If there is no error returned by the http.Get(link) call, it indicates that the link is up and the link with which the function is called gets returned through channel c to be used again in the infinite loop.

Output

A continuous list of strings indicating if the webpages in the links slice of strings are up / down, until there is an interrupt signal from the keyboard (Ctrl+C).

Example

https://golang.org is up!
https://google.com is up!
https://facebook.com is up!
https://amazon.com is up!
https://golang.org is up!
https://google.com is up!
https://facebook.com is up!

How-To

Build and Run the Application

go build main.go
./main

Test

no tests were developed for this application

Notes

N/A

DPontes / Go-Channels