learn_golang/learn_go_with_tests/concurrency/CheckWebsites.go

package concurrency

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 {
		// anonymous function call required because go routines must call
		// a function to start. An anonymous function maintains access to
		// the lexical scope in which they are defined - all the variables
		// that are available at the point when you declare the anonymous
		//function are also available in the body of the function.
		// url := url // create a new variable to avoid capturing the loop variable.
		// go func() {
		// 	results[url] = wc(url)
		// }()
		go func(u string) {
			resultChannel <- result{u, wc(u)} // send statement
		}(url) // or just pass by value to give the func it's own url
	}

	for i := 0; i < len(urls); i++ {
		r := <-resultChannel // receive statement
		results[r.string] = r.bool
	}

	return results
}