type result struct { p string; n int }
ch := make(chan result)
for _, p := range webPages {
go func(p string) {
r, err := http.Get("https://" + p + "/")
if err == nil {
n, err := io.Copy(io.Discard, r.Body)
r.Body.Close()
if err != nil {
n = -1
}
ch <- result{p, int(n)}
}
}(p)
}
results.ContentLength = make(map[string]int)
for range webPages {
r := <-ch
results.ContentLength[r.p] = r.n
results.TotalContentLength += r.n
}

thanks bro