added iota constants

concurrency/basic_channel_error_handling/main.go

@@ -0,0 +1,52 @@
+package main
+
+import (
+	"fmt"
+	"math/rand"
+	"time"
+)
+
+func fetchAll() error {
+	var N = 4
+	quit := make(chan bool)
+	errc := make(chan error)
+	done := make(chan error)
+	for i := 0; i < N; i++ {
+		go func(i int) {
+			// dummy fetch
+			time.Sleep(time.Duration(rand.Intn(100)) * time.Millisecond)
+			err := error(nil)
+			if rand.Intn(2) == 0 {
+				err = fmt.Errorf("goroutine %d's error returned", i)
+			}
+			ch := done // we'll send to done if nil error and to errc otherwise
+			if err != nil {
+				ch = errc
+			}
+			select {
+			case ch <- err:
+				return
+			case <-quit:
+				return
+			}
+		}(i)
+	}
+	count := 0
+	for {
+		select {
+		case err := <-errc:
+			close(quit)
+			return err
+		case <-done:
+			count++
+			if count == N {
+				return nil // got all N signals, so there was no error
+			}
+		}
+	}
+}
+
+func main() {
+	rand.Seed(time.Now().UnixNano())
+	fmt.Println(fetchAll())
+}

idiom/iota_const/main.go

@@ -0,0 +1,22 @@
+package main
+
+import "github.com/davecgh/go-spew/spew"
+
+type FeedLockLinkType int
+
+const (
+	Racing FeedLockLinkType = iota
+	Market
+)
+
+var feedLockLinkTypes = [...]string{
+	"racing.Races.raceID",
+	"racing.Markets.marketID",
+}
+
+func (f FeedLockLinkType) String() string { return feedLockLinkTypes[f] }
+
+func main() {
+	test := FeedLockLinkType(Racing)
+	spew.Dump(test)
+}