add ch14

ch14/2/ch14_2.go

@@ -0,0 +1,36 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"math/rand"
+	"time"
+)
+
+type RandSum struct{}
+
+func main() {
+	sum := 0
+	ctx, cancel := context.WithTimeout(context.Background(), time.Duration(2)*time.Second)
+	defer cancel()
+	start := time.Now()
+	i := 0
+outLoop:
+	for {
+		select {
+		case <-ctx.Done():
+			ctx = context.WithValue(ctx, RandSum{}, "timeout")
+			break outLoop
+		default:
+			i++
+			randNum := rand.Int() % 100_000_000
+			//fmt.Printf("Randnum is %d\n", randNum)
+			sum = sum + randNum
+			if randNum == 1234 {
+				ctx = context.WithValue(ctx, RandSum{}, "number reached")
+				break outLoop
+			}
+		}
+	}
+	fmt.Printf("Sum is %d after %v; iterations - %d; cause - %s\n", sum, time.Since(start), i, ctx.Value(RandSum{}))
+}