added iterator

concurrency/iterator/main.go

@@ -0,0 +1,24 @@
+package main
+
+import "fmt"
+
+// Generator func which produces data which might be computationally expensive.
+func fib(n int) chan int {
+	c := make(chan int)
+	go func() {
+		for i, j := 0, 1; i < n; i, j = i+j, i {
+			c <- i
+		}
+		close(c)
+	}()
+	return c
+}
+
+func main() {
+	// fib returns the fibonacci numbers lesser than 1000
+	for i := range fib(1000) {
+		// Consumer which consumes the data produced by the generator, which further does some extra computations
+		v := i * i
+		fmt.Println(v)
+	}
+}