Praktiska uzdevums: īstenot funkciju FastestSearcher, kas paralēli veic vairāku meklētāju testēšanu un atgriež visātrākā nosaukumu, atbildes laiku un kļūdu (ja vismaz viens atgriež kļūdu).

go package main

import ( "errors" "fmt" "sync" "time" )

type SearchResult struct { Name string Duration time.Duration Err error }

// FastestSearcher запускает параллельно несколько функций поиска и возвращает имя самого быстрого, время и ошибку. func FastestSearcher(searchers map[string]func() error) (string, time.Duration, error) { results := make(chan SearchResult, len(searchers)) var wg sync.WaitGroup

for name, searchFunc := range searchers {
	wg.Add(1)
	go func(n string, f func() error) {
		defer wg.Done()
		start := time.Now()
		err := f()
		dur := time.Since(start)
		results <- SearchResult{Name: n, Duration: dur, Err: err}
	}(name, searchFunc)
}

wg.Wait()
close(results)

var fastest SearchResult
var hasError bool
first := true

for res := range results {
	if res.Err != nil {
		hasError = true
	}
	if first || res.Duration < fastest.Duration {
		fastest = res
		first = false
	}
}

if hasError {
	return fastest.Name, fastest.Duration, errors.New("at least one searcher returned an error")
}
return fastest.Name, fastest.Duration, nil

}

func main() { searchers := map[string]func() error{ "Google": func() error { time.Sleep(100 * time.Millisecond) return nil }, "Bing": func() error { time.Sleep(80 * time.Millisecond) return nil }, "Yahoo": func() error { time.Sleep(120 * time.Millisecond) return errors.New("timeout") }, }

name, duration, err := FastestSearcher(searchers)
fmt.Printf("Fastest: %s, Duration: %v, Error: %v\n", name, duration, err)

}