update book code

eBook/exercises/chapter_9/main_greetings.go

@@ -0,0 +1,22 @@
+package main
+
+import (
+	"fmt"
+	"./greetings/greetings"
+)
+
+func main() {
+	name := "James"
+	fmt.Println(greetings.GoodDay(name))
+	fmt.Println(greetings.GoodNight(name))
+	
+	if greetings.IsAM() {
+		fmt.Println("Good morning", name)
+	} else if greetings.IsAfternoon(){
+		fmt.Println("Good afternoon", name)
+	} else if greetings.IsEvening(){
+		fmt.Println("Good evening", name)
+	} else {
+		fmt.Println("Good night", name)
+	}
+}