golang using timeouts with channels

Question

I am using goroutines/channels to check if list of urls are reachable. Here is my code. This seems to always return true. Why is the timeout case not getting executed? The g

Answer 1

The reason this always returns true is you are calling check(u) within your select statement. You need to call it within a go routine and then use a select to either wait for the result or timeout.

In case you want to check the reachability of multiple URLs in parallel you need to restructure your code.

First create a function which checks the reachability of one URL:

func IsReachable(url string) bool {
    ch := make(chan bool, 1)
    go func() { ch <- check(url) }()
    select {
    case reachable := <-ch:
        return reachable
    case <-time.After(time.Second):
        // call timed out
        return false
    }
}

Then call this function from a loop:

urls := []string{"url1", "url2", "url3"}
for _, url := range urls {
    go func() { fmt.Println(IsReachable(url)) }()
}

Play