update book code

eBook/examples/chapter_6/fibonacci.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+func main() {
+	result := 0
+	start := time.Now()
+	for i:=0; i <= 25; i++ {
+		result = fibonacci(i) 
+		fmt.Printf("fibonacci(%d) is: %d\n", i, result)
+	}
+	end := time.Now()
+	delta := end.Sub(start)
+	fmt.Printf("longCalculation took this amount of time: %s\n", delta) 
+}
+
+func fibonacci(n int) (res int) {
+	if n <= 1 {
+		res = 1
+	} else {
+		res = fibonacci(n-1) + fibonacci(n-2)
+	}
+	return
+}
+/* Output:
+fibonacci(0) is: 1
+fibonacci(1) is: 1
+fibonacci(2) is: 2
+fibonacci(3) is: 3
+fibonacci(4) is: 5
+fibonacci(5) is: 8
+fibonacci(6) is: 13
+fibonacci(7) is: 21
+fibonacci(8) is: 34
+fibonacci(9) is: 55
+fibonacci(10) is: 89
+fibonacci(11) is: 144
+fibonacci(12) is: 233
+fibonacci(13) is: 377
+fibonacci(14) is: 610
+fibonacci(15) is: 987
+fibonacci(16) is: 1597
+fibonacci(17) is: 2584
+fibonacci(18) is: 4181
+fibonacci(19) is: 6765
+fibonacci(20) is: 10946
+fibonacci(21) is: 17711
+fibonacci(22) is: 28657
+fibonacci(23) is: 46368
+fibonacci(24) is: 75025
+fibonacci(25) is: 121393
+longCalculation took this amount of time: 3.0001ms
+*/