update book code

eBook/exercises/chapter_9/greetings/greetings.go

@@ -0,0 +1,27 @@
+package greetings
+
+import "time"
+
+func GoodDay(name string) string {
+	return "Good Day " + name
+}
+
+func GoodNight(name string) string{
+	return "Good Night " + name
+}
+
+func IsAM() bool {
+	localTime := time.Now()
+	return localTime.Hour() <= 12
+}
+
+func IsAfternoon() bool {
+	localTime := time.Now()
+	return localTime.Hour() <= 18
+}
+
+func IsEvening() bool {
+	localTime := time.Now()
+	return localTime.Hour() <= 22
+}
+