added iterator example

concurrency/iterator_error_handling/main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"fmt"
 	"time"
 
 	"github.com/davecgh/go-spew/spew"
@@ -21,7 +22,44 @@ func dummyFetchUrl(url string) *FetchResult {
 	}
 }
 
-func main() {
-	r := dummyFetchUrl("http://www.google.com")
-	spew.Dump(r)
+func concurrentFetch(urls []string) <-chan *FetchResult {
+	rChan := make(chan *FetchResult, len(urls))
+	for _, url := range urls {
+		go func(url string) {
+			result := dummyFetchUrl(url)
+			rChan <- result
+		}(url)
+	}
+	return rChan
+}
+
+func main() {
+	// mock the urls
+	urls := []string{
+		"test1",
+		"test2",
+		"test3",
+		"test4",
+		"test5",
+		"test6",
+	}
+
+	// this is a prefered method
+	chanResults := concurrentFetch(urls)
+	for i := 0; i < len(urls); i++ {
+		select {
+		case c := <-chanResults:
+			spew.Dump(c)
+		}
+	}
+
+	// i := 0
+	// for v := range concurrentFetch(urls) {
+	// 	spew.Dump(i, v)
+	// 	i++
+	// 	if i == len(urls) {
+	// 		break
+	// 	}
+	// }
+	fmt.Println("All my things are done")
 }