implemented observer pattern

behavioral/observer/observer.go

@@ -0,0 +1,38 @@
+package observer
+
+import (
+	"fmt"
+)
+
+type Observer interface {
+	Notify(string)
+}
+
+type Publisher struct {
+	ObserverList []Observer
+}
+
+func (p *Publisher) Subscribe(o Observer) {
+	p.ObserverList = append(p.ObserverList, o)
+}
+
+func (p *Publisher) Unsubscribe(o Observer) {
+	var index int
+	for i, v := range p.ObserverList {
+		if v == o {
+			index = i
+			break
+		}
+	}
+
+	p.ObserverList = append(p.ObserverList[:index], p.ObserverList[index + 1:]...)
+}
+
+func (p *Publisher) Publish(m string) {
+	fmt.Println("Got new message! Publishing...")
+	for _, o := range p.ObserverList {
+		o.Notify(m)
+	}
+	fmt.Println("Puplished!")
+}
+