diff --git a/.golangci.yml b/.golangci.yml
index 65be680b72..7e9642bfee 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -4,6 +4,7 @@ run:
     - ^.*\.(pb|y)\.go$
   skip-dirs:
     - "vendor$"
+    - "pkg/app/piped/executor/analysis/mannwhitney"
 
 linters:
   disable-all: true
diff --git a/pkg/app/ops/planpreviewoutputcleaner/cleaner.go b/pkg/app/ops/planpreviewoutputcleaner/cleaner.go
index 96ca56acc0..b490a9bc3c 100644
--- a/pkg/app/ops/planpreviewoutputcleaner/cleaner.go
+++ b/pkg/app/ops/planpreviewoutputcleaner/cleaner.go
@@ -28,7 +28,6 @@ import (
 const (
 	outputTTL    = 48 * time.Hour
 	cronSchedule = "0 9 * * *" // Run at 09:00 every day.
-	interval     = 24 * time.Hour
 	prefix       = "command-output/"
 )
 
diff --git a/pkg/app/piped/livestatestore/cloudrun/store.go b/pkg/app/piped/livestatestore/cloudrun/store.go
index 07ce50dfaa..f445f1406d 100644
--- a/pkg/app/piped/livestatestore/cloudrun/store.go
+++ b/pkg/app/piped/livestatestore/cloudrun/store.go
@@ -17,9 +17,9 @@ package cloudrun
 import (
 	"context"
 	"fmt"
-	"sync/atomic"
 	"time"
 
+	"go.uber.org/atomic"
 	"go.uber.org/zap"
 
 	provider "github.com/pipe-cd/pipecd/pkg/app/piped/platformprovider/cloudrun"
diff --git a/pkg/app/server/grpcapi/grpcapi.go b/pkg/app/server/grpcapi/grpcapi.go
index 420c6887b6..1e1acfae97 100644
--- a/pkg/app/server/grpcapi/grpcapi.go
+++ b/pkg/app/server/grpcapi/grpcapi.go
@@ -184,10 +184,6 @@ func gRPCStoreError(err error, msg string) error {
 	return status.Error(codes.Internal, fmt.Sprintf("Failed to %s", msg))
 }
 
-func makeUnregisteredAppsCacheKey(projectID string) string {
-	return fmt.Sprintf("HASHKEY:UNREGISTERED_APPS:%s", projectID)
-}
-
 func getPipedStatus(cs cache.Cache, id string) (model.Piped_ConnectionStatus, error) {
 	pipedStatus, err := cs.Get(id)
 	if errors.Is(err, cache.ErrNotFound) {