Add lint option to Makefile and fix lint issues

Author: Rulox

CONTRIBUTING.md

@@ -67,3 +67,4 @@ Note: if you’d like to implement a new feature, please consider creating a fea
 * Run `gofmt` over your code to automatically resolve a lot of style issues. Most editors support this running automatically when saving a code file.
 * Run `go lint` and `go vet` on your code too to catch any other issues.
 * Follow this guide on some good practice and idioms for Go -  https://github.com/golang/go/wiki/CodeReviewComments
+* To check for extra issues, install [golangci-lint](https://github.com/golangci/golangci-lint) and run `make lint` or `golangci-lint run`

Makefile

@@ -11,6 +11,9 @@ else
 	go test ./...
 endif
 
+lint:
+	golangci-lint run
+
 compile: test
 ifeq ($(BUILD_IN_CONTAINER),1)
 	$(GO_DOCKER_RUN) $(GOLANG_CONTAINER) go build -o /build_output/nginx-asg-sync

cmd/sync/aws.go

@@ -91,9 +91,7 @@ func (client *AWSClient) getInstancesOfAutoscalingGroup(group *autoscaling.Group
 		return result, err
 	}
 	for _, res := range resp.Reservations {
-		for _, ins := range res.Instances {
-			result = append(result, ins)
-		}
+		result = append(result, res.Instances...)
 	}
 
 	return result, nil

cmd/sync/main.go

@@ -145,7 +145,12 @@ func main() {
 func createAWSClient(region string) *AWSClient {
 	httpClient := &http.Client{Timeout: connTimeoutInSecs * time.Second}
 	cfg := &aws.Config{Region: aws.String(region), HTTPClient: httpClient}
-	session := session.New(cfg)
+	session, err := session.NewSession(cfg)
+
+	if err != nil {
+		log.Printf("Error while creating AWS Client: %v", err)
+	}
+
 	svcAutoscaling := autoscaling.New(session)
 	svcEC2 := ec2.New(session)
 	return NewAWSClient(svcEC2, svcAutoscaling)