paulhtrott/pt-learning-go: monitor.go; 18 LoC

Found a possible issue in [paulhtrott/pt-learning-go](https://www.github.com/paulhtrott/pt-learning-go) at [monitor.go](https://github.com/paulhtrott/pt-learning-go/blob/5ca60e61763d47afb2b3d630cee7ca05aa87a03c/monitor.go#L41-L58)

Below is the message reported by the analyzer for this snippet of code. Beware that the analyzer only reports the first issue it finds, so please do not limit your consideration to the contents of the below message.

> range-loop variable i used in defer or goroutine at line 56

[Click here to see the code in its original context.](https://github.com/paulhtrott/pt-learning-go/blob/5ca60e61763d47afb2b3d630cee7ca05aa87a03c/monitor.go#L41-L58)

Click here to show the 18 line(s) of Go which triggered the analyzer.

```go
for i, site := range sites {
// Launch each retrieval in a go routine. This makes each request concurrent
go func(index int, site string) {
defer wg.Done()

// start a timer for this request
begin := time.Now()

// Retrieve the site
resp, err := http.Get(site)
if err != nil {
fmt.Println(site, err)
return
}

fmt.Printf("%d Site %q took %s to retrieve with status code of %d.\n", i, site, time.Since(begin), resp.StatusCode)
}(i, site)
}

```

Leave a reaction on this issue to contribute to the project by classifying this instance as a **Bug** :-1:, **Mitigated** :+1:, or **Desirable Behavior** :rocket:
See the descriptions of the classifications [here](https://github.com/github-vet/rangeclosure-findings#how-can-i-help) for more information.

commit ID: 5ca60e61763d47afb2b3d630cee7ca05aa87a03c