add gocritic/ruleguard checks back again, cleanup code. (#13665)

- remove some duplicated code
- reported a bug, separately fixed in #13664
- using strings.ReplaceAll() when needed
- using filepath.ToSlash() use when needed
- remove all non-Go style comments from the codebase

Co-authored-by: Aditya Manthramurthy <donatello@users.noreply.github.com>

internal/event/target/kafka_scram_client_contrib.go

@@ -25,13 +25,14 @@ import (
 )
 
 func initScramClient(args KafkaArgs, config *sarama.Config) {
-	if args.SASL.Mechanism == "sha512" {
+	switch args.SASL.Mechanism {
+	case "sha512":
 		config.Net.SASL.SCRAMClientGeneratorFunc = func() sarama.SCRAMClient { return &XDGSCRAMClient{HashGeneratorFcn: KafkaSHA512} }
 		config.Net.SASL.Mechanism = sarama.SASLMechanism(sarama.SASLTypeSCRAMSHA512)
-	} else if args.SASL.Mechanism == "sha256" {
+	case "sha256":
 		config.Net.SASL.SCRAMClientGeneratorFunc = func() sarama.SCRAMClient { return &XDGSCRAMClient{HashGeneratorFcn: KafkaSHA256} }
 		config.Net.SASL.Mechanism = sarama.SASLMechanism(sarama.SASLTypeSCRAMSHA256)
-	} else {
+	default:
 		// default to PLAIN
 		config.Net.SASL.Mechanism = sarama.SASLMechanism(sarama.SASLTypePlaintext)
 	}

internal/event/target/mqtt.go

@@ -272,10 +272,8 @@ func NewMQTTTarget(id string, args MQTTArgs, doneCh <-chan struct{}, loggerOnce
 			// Start replaying events from the store.
 			go sendEvents(target, eventKeyCh, doneCh, target.loggerOnce)
 		}
-	} else {
-		if token.Wait() && token.Error() != nil {
-			return target, token.Error()
-		}
+	} else if token.Wait() && token.Error() != nil {
+		return target, token.Error()
 	}
 	return target, nil
 }

internal/event/target/nats.go

@@ -172,6 +172,7 @@ func (n NATSArgs) connectStan() (stan.Conn, error) {
 	}
 
 	var addressURL string
+	//nolint:gocritic
 	if n.Username != "" && n.Password != "" {
 		addressURL = scheme + "://" + n.Username + ":" + n.Password + "@" + n.Address.String()
 	} else if n.Token != "" {
@@ -219,18 +220,14 @@ func (target *NATSTarget) IsActive() (bool, error) {
 	if target.args.Streaming.Enable {
 		if target.stanConn == nil || target.stanConn.NatsConn() == nil {
 			target.stanConn, connErr = target.args.connectStan()
-		} else {
-			if !target.stanConn.NatsConn().IsConnected() {
-				return false, errNotConnected
-			}
+		} else if !target.stanConn.NatsConn().IsConnected() {
+			return false, errNotConnected
 		}
 	} else {
 		if target.natsConn == nil {
 			target.natsConn, connErr = target.args.connectNats()
-		} else {
-			if !target.natsConn.IsConnected() {
-				return false, errNotConnected
-			}
+		} else if !target.natsConn.IsConnected() {
+			return false, errNotConnected
 		}
 	}