Fix #254 typo error (#255)

eBook/examples/chapter_9/book/package_test.go

@@ -9,6 +9,6 @@ func main() {
     var test1 string
     test1 = pack1.ReturnStr()
     fmt.Printf("ReturnStr from package1: %s\n", test1)
-    fmt.Printf(“Integer from package1: %d\n”, pack1.Pack1Int)
+    fmt.Printf("Integer from package1: %d\n", pack1.Pack1Int)
     // fmt.Printf(“Float from package1: %f\n”, pack1.pack1Float)
 }