update book code

eBook/examples/chapter_4/function_calls_function.go

@@ -1,15 +1,15 @@
-package main
-var a string
-func main() {
-	a = "G"
-	print(a)
-	f1()
-}
-func f1() {
-	a := "O"
-	print(a)
-	f2()
-}
-func f2() {
-	print(a)
+package main
+var a string
+func main() {
+	a = "G"
+	print(a)
+	f1()
+}
+func f1() {
+	a := "O"
+	print(a)
+	f2()
+}
+func f2() {
+	print(a)
 }