Fix lint and add lint doc in README.md

Author: godsarmy

README.md

@@ -4,3 +4,5 @@ golang-design-patterns
 A collection of design patterns implemented in golang.
 
 Prefer to build use golang >= 1.18
+
+Install [golangci-lint] (https://github.com/golangci/golangci-lint) for lint.

cmd/chain/main.go

@@ -34,7 +34,7 @@ func (p *ConcreteHandler2) handle(request int) {
 
 // implementor 3
 type ConcreteHandler3 struct {
-	successor Handler
+	successor Handler //nolint:unused
 }
 
 func (p *ConcreteHandler3) handle(request int) {

cmd/command/main.go

@@ -27,6 +27,6 @@ func main() {
 	var ren1, ren2 MoveFileCommand
 	ren2, list = list[len(list)-1], list[:len(list)-1]
 	ren2.undo()
-	ren1, list = list[len(list)-1], list[:len(list)-1]
+	ren1, _ = list[len(list)-1], list[:len(list)-1]
 	ren1.undo()
 }

cmd/composite/main.go

@@ -22,6 +22,7 @@ func (p *CompositeGraphic) add(graphic Graphic) {
 	p.childGraphics = append(p.childGraphics, graphic)
 }
 
+//nolint:unused
 func (p *CompositeGraphic) remove(graphic Graphic) {
 	new_list := []Graphic{}
 	for _, obj := range p.childGraphics {

cmd/proxy/main.go

@@ -29,6 +29,7 @@ func (p *Proxy) work() {
 	} else {
 		time.Sleep(1 * time.Second)
 		fmt.Println("Sales Manager is busy")
+		p.Sales.work()
 	}
 }
 

cmd/template_method/main.go

@@ -22,13 +22,13 @@ func (p *Template) templateMethod() {
 }
 
 func (p IntList) modify_list() {
-	for i, _ := range []int(p) {
+	for i := range []int(p) {
 		p[i] *= 2
 	}
 }
 
 func (p ByteList) modify_list() {
-	for i, _ := range []byte(p) {
+	for i := range []byte(p) {
 		p[i]++
 	}
 }