Modify strategy pattern

strategy/strategy.go

@@ -0,0 +1,25 @@
+package strategy
+
+type Operator interface {
+	Apply(int, int) int
+}
+
+type Operation struct {
+	Operator Operator
+}
+
+func (o *Operation) Operate(leftValue, rightValue int) int {
+	return o.Operator.Apply(leftValue, rightValue)
+}
+
+type Multiplication struct{}
+
+func (Multiplication) Apply(lval, rval int) int {
+	return lval * rval
+}
+
+type Addition struct{}
+
+func (Addition) Apply(lval, rval int) int {
+	return lval + rval
+}