Add template design pattern

template.go

@@ -0,0 +1,48 @@
+// In Template pattern, an abstract struct exposes defined way(s)/template(s)
+// to execute its methods. This pattern comes under behavior pattern category.
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+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 Pow struct{}
+
+func (_ Pow) Apply(lval, rval int) int {
+	return int(math.Pow(float64(lval), float64(rval)))
+}
+
+func main() {
+	mult := Operation{
+		Operator: Multiplication{},
+	}
+
+	// Outputs 15
+	fmt.Println(mult.Operate(3, 5))
+
+	pow := Operation{
+		Operator: Pow{},
+	}
+
+	// Outputs 243
+	fmt.Println(pow.Operate(3, 5))
+}