package main type WebsiteChecker func(string) bool type result struct { string bool } func CheckWebsites(wc WebsiteChecker, urls []string) map[string]bool { results := make(map[string]bool) resultChannel := make(chan result) for _, url := range urls { go func(u string) { resultChannel <- result{u, wc(u)} }(url) } for i := 0; i < len(urls); i++ { r := <-resultChannel results[r.string] = r.bool } return results }