diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b863a1d..54cec25 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -17,7 +17,7 @@ jobs:
 
     strategy:
       matrix:
-        go-version: [1.17.x]
+        go-version: [1.21.x]
 
     steps:
       - uses: actions/setup-go@v2
@@ -60,7 +60,7 @@ jobs:
       - name: golangci-lint check
         uses: golangci/golangci-lint-action@v3
         with:
-          version: v1.44.2
+          version: v1.55.2
           args: --timeout=5m
           working-directory: src/github.com/fuweid/embedshim
 
@@ -70,7 +70,7 @@ jobs:
   # based on https://github.com/containerd/project-checks/blob/main/action.yml
   project:
     name: Project Checks
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-22.04
     timeout-minutes: 5
 
     steps:
@@ -128,7 +128,7 @@ jobs:
       # ubuntu-22.04 is used to test cgroupv2
       # ubuntu-20.04 is for cgroupv1 (common)
       matrix:
-        go-version: [1.17.x]
+        go-version: [1.21.x]
         os: [ubuntu-20.04, ubuntu-22.04]
 
     runs-on: ${{ matrix.os }}
diff --git a/.golangci.yml b/.golangci.yml
index 1aa4194..aa6f243 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -19,8 +19,6 @@
 # 
 linters:
   enable:
-    - structcheck
-    - varcheck
     - staticcheck
     - unconvert
     - gofmt
diff --git a/cmd/embedshim-runcext/app.go b/cmd/embedshim-runcext/app.go
index 0b5d91c..b7c9811 100644
--- a/cmd/embedshim-runcext/app.go
+++ b/cmd/embedshim-runcext/app.go
@@ -52,10 +52,7 @@ func newApp() *cli.App {
 	}
 	app.Commands = append(app.Commands, execCommand)
 	app.Before = func(_ *cli.Context) error {
-		if err := reaper.SetSubreaper(1); err != nil {
-			return err
-		}
-		return nil
+		return reaper.SetSubreaper(1)
 	}
 	return app
 }
diff --git a/delete_state.go b/delete_state.go
index a477f43..21a6602 100644
--- a/delete_state.go
+++ b/delete_state.go
@@ -29,46 +29,46 @@ import (
 type deletedState struct {
 }
 
-func (s *deletedState) Pause(ctx context.Context) error {
+func (s *deletedState) Pause(_ context.Context) error {
 	return fmt.Errorf("cannot pause a deleted process")
 }
 
-func (s *deletedState) Resume(ctx context.Context) error {
+func (s *deletedState) Resume(_ context.Context) error {
 	return fmt.Errorf("cannot resume a deleted process")
 }
 
-func (s *deletedState) Update(context context.Context, r *google_protobuf.Any) error {
+func (s *deletedState) Update(_ context.Context, _ *google_protobuf.Any) error {
 	return fmt.Errorf("cannot update a deleted process")
 }
 
-func (s *deletedState) Checkpoint(ctx context.Context, r *CheckpointConfig) error {
+func (s *deletedState) Checkpoint(_ context.Context, _ *CheckpointConfig) error {
 	return fmt.Errorf("cannot checkpoint a deleted process")
 }
 
-func (s *deletedState) Resize(ws console.WinSize) error {
+func (s *deletedState) Resize(_ console.WinSize) error {
 	return fmt.Errorf("cannot resize a deleted process")
 }
 
-func (s *deletedState) Start(ctx context.Context) error {
+func (s *deletedState) Start(_ context.Context) error {
 	return fmt.Errorf("cannot start a deleted process")
 }
 
-func (s *deletedState) Delete(ctx context.Context) error {
+func (s *deletedState) Delete(_ context.Context) error {
 	return fmt.Errorf("cannot delete a deleted process: %w", errdefs.ErrNotFound)
 }
 
-func (s *deletedState) Kill(ctx context.Context, sig uint32, all bool) error {
+func (s *deletedState) Kill(_ context.Context, _ uint32, _ bool) error {
 	return fmt.Errorf("cannot kill a deleted process: %w", errdefs.ErrNotFound)
 }
 
-func (s *deletedState) SetExited(status int) {
+func (s *deletedState) SetExited(_ int) {
 	// no op
 }
 
-func (s *deletedState) Exec(ctx context.Context, id string, opts runtime.ExecOpts) (runtime.Process, error) {
+func (s *deletedState) Exec(_ context.Context, _ string, _ runtime.ExecOpts) (runtime.Process, error) {
 	return nil, fmt.Errorf("cannot exec in a deleted state")
 }
 
-func (s *deletedState) Status(ctx context.Context) (string, error) {
+func (s *deletedState) Status(_ context.Context) (string, error) {
 	return "stopped", nil
 }
diff --git a/exec_process.go b/exec_process.go
index a654e41..1859f7d 100644
--- a/exec_process.go
+++ b/exec_process.go
@@ -108,7 +108,7 @@ func (e *execProcess) setExited(status int) {
 	close(e.waitBlock)
 }
 
-func (e *execProcess) CloseIO(ctx context.Context) error {
+func (e *execProcess) CloseIO(_ context.Context) error {
 	if stdin := e.Stdin(); stdin != nil {
 		if err := stdin.Close(); err != nil {
 			return err
@@ -214,7 +214,7 @@ func (e *execProcess) Kill(ctx context.Context, sig uint32, _ bool) error {
 	return e.execState.Kill(ctx, sig, false)
 }
 
-func (e *execProcess) kill(ctx context.Context, sig uint32, _ bool) error {
+func (e *execProcess) kill(_ context.Context, sig uint32, _ bool) error {
 	pid := e.pid.get()
 	switch {
 	case pid == 0:
diff --git a/exec_process_state.go b/exec_process_state.go
index d13c26e..c9602bc 100644
--- a/exec_process_state.go
+++ b/exec_process_state.go
@@ -82,7 +82,7 @@ func (s *execCreatedState) SetExited(status int) {
 	}
 }
 
-func (s *execCreatedState) Status(ctx context.Context) (string, error) {
+func (s *execCreatedState) Status(_ context.Context) (string, error) {
 	return "created", nil
 }
 
@@ -104,11 +104,11 @@ func (s *execRunningState) Resize(ws console.WinSize) error {
 	return s.p.resize(ws)
 }
 
-func (s *execRunningState) Start(ctx context.Context) error {
+func (s *execRunningState) Start(_ context.Context) error {
 	return fmt.Errorf("cannot start a running process")
 }
 
-func (s *execRunningState) Delete(ctx context.Context) error {
+func (s *execRunningState) Delete(_ context.Context) error {
 	return fmt.Errorf("cannot delete a running process")
 }
 
@@ -124,7 +124,7 @@ func (s *execRunningState) SetExited(status int) {
 	}
 }
 
-func (s *execRunningState) Status(ctx context.Context) (string, error) {
+func (s *execRunningState) Status(_ context.Context) (string, error) {
 	return "running", nil
 }
 
@@ -142,11 +142,11 @@ func (s *execStoppedState) transition(name string) error {
 	return nil
 }
 
-func (s *execStoppedState) Resize(ws console.WinSize) error {
+func (s *execStoppedState) Resize(_ console.WinSize) error {
 	return fmt.Errorf("cannot resize a stopped container")
 }
 
-func (s *execStoppedState) Start(ctx context.Context) error {
+func (s *execStoppedState) Start(_ context.Context) error {
 	return fmt.Errorf("cannot start a stopped process")
 }
 
@@ -162,10 +162,10 @@ func (s *execStoppedState) Kill(ctx context.Context, sig uint32, all bool) error
 	return s.p.kill(ctx, sig, all)
 }
 
-func (s *execStoppedState) SetExited(status int) {
+func (s *execStoppedState) SetExited(_ int) {
 	// no op
 }
 
-func (s *execStoppedState) Status(ctx context.Context) (string, error) {
+func (s *execStoppedState) Status(_ context.Context) (string, error) {
 	return "stopped", nil
 }
diff --git a/init_process.go b/init_process.go
index 3bbed80..04b02e1 100644
--- a/init_process.go
+++ b/init_process.go
@@ -437,7 +437,7 @@ func (p *initProcess) exec(ctx context.Context, execID string, opts runtime.Exec
 }
 
 // Checkpoint the init process
-func (p *initProcess) Checkpoint(ctx context.Context, r *CheckpointConfig) error {
+func (p *initProcess) Checkpoint(_ context.Context, _ *CheckpointConfig) error {
 	return fmt.Errorf("checkpoint not implemented yet")
 }
 
diff --git a/init_process_state.go b/init_process_state.go
index 57820df..dd0aaee 100644
--- a/init_process_state.go
+++ b/init_process_state.go
@@ -69,11 +69,11 @@ func (s *createdState) transition(name string) error {
 	return nil
 }
 
-func (s *createdState) Pause(ctx context.Context) error {
+func (s *createdState) Pause(_ context.Context) error {
 	return fmt.Errorf("cannot pause task in created state")
 }
 
-func (s *createdState) Resume(ctx context.Context) error {
+func (s *createdState) Resume(_ context.Context) error {
 	return fmt.Errorf("cannot resume task in created state")
 }
 
@@ -81,7 +81,7 @@ func (s *createdState) Update(ctx context.Context, r *google_protobuf.Any) error
 	return s.p.update(ctx, r)
 }
 
-func (s *createdState) Checkpoint(ctx context.Context, r *CheckpointConfig) error {
+func (s *createdState) Checkpoint(_ context.Context, _ *CheckpointConfig) error {
 	return fmt.Errorf("cannot checkpoint a task in created state")
 }
 
@@ -115,7 +115,7 @@ func (s *createdState) Exec(ctx context.Context, id string, opts runtime.ExecOpt
 	return s.p.exec(ctx, id, opts)
 }
 
-func (s *createdState) Status(ctx context.Context) (string, error) {
+func (s *createdState) Status(_ context.Context) (string, error) {
 	return "created", nil
 }
 
@@ -135,11 +135,11 @@ func (s *runningState) transition(name string) error {
 	return nil
 }
 
-func (s *runningState) Pause(ctx context.Context) error {
+func (s *runningState) Pause(_ context.Context) error {
 	return fmt.Errorf("pause not implemented yet")
 }
 
-func (s *runningState) Resume(ctx context.Context) error {
+func (s *runningState) Resume(_ context.Context) error {
 	return fmt.Errorf("cannot resume a running process")
 }
 
@@ -147,15 +147,15 @@ func (s *runningState) Update(ctx context.Context, r *google_protobuf.Any) error
 	return s.p.update(ctx, r)
 }
 
-func (s *runningState) Checkpoint(ctx context.Context, r *CheckpointConfig) error {
+func (s *runningState) Checkpoint(_ context.Context, _ *CheckpointConfig) error {
 	return fmt.Errorf("checkpoint not implemented yet")
 }
 
-func (s *runningState) Start(ctx context.Context) error {
+func (s *runningState) Start(_ context.Context) error {
 	return fmt.Errorf("cannot start a running process")
 }
 
-func (s *runningState) Delete(ctx context.Context) error {
+func (s *runningState) Delete(_ context.Context) error {
 	return fmt.Errorf("cannot delete a running process")
 }
 
@@ -175,7 +175,7 @@ func (s *runningState) Exec(ctx context.Context, id string, opts runtime.ExecOpt
 	return s.p.exec(ctx, id, opts)
 }
 
-func (s *runningState) Status(ctx context.Context) (string, error) {
+func (s *runningState) Status(_ context.Context) (string, error) {
 	return "running", nil
 }
 
@@ -195,11 +195,11 @@ func (s *pausedState) transition(name string) error {
 	return nil
 }
 
-func (s *pausedState) Pause(ctx context.Context) error {
+func (s *pausedState) Pause(_ context.Context) error {
 	return fmt.Errorf("cannot pause a paused container")
 }
 
-func (s *pausedState) Resume(ctx context.Context) error {
+func (s *pausedState) Resume(_ context.Context) error {
 	return fmt.Errorf("resume not implemented yet")
 }
 
@@ -207,15 +207,15 @@ func (s *pausedState) Update(ctx context.Context, r *google_protobuf.Any) error
 	return s.p.update(ctx, r)
 }
 
-func (s *pausedState) Checkpoint(ctx context.Context, r *CheckpointConfig) error {
+func (s *pausedState) Checkpoint(_ context.Context, _ *CheckpointConfig) error {
 	return fmt.Errorf("checkpoint not implemented yet")
 }
 
-func (s *pausedState) Start(ctx context.Context) error {
+func (s *pausedState) Start(_ context.Context) error {
 	return fmt.Errorf("cannot start a paused process")
 }
 
-func (s *pausedState) Delete(ctx context.Context) error {
+func (s *pausedState) Delete(_ context.Context) error {
 	return fmt.Errorf("cannot delete a paused process")
 }
 
@@ -235,11 +235,11 @@ func (s *pausedState) SetExited(status int) {
 	}
 }
 
-func (s *pausedState) Exec(ctx context.Context, id string, opts runtime.ExecOpts) (runtime.Process, error) {
+func (s *pausedState) Exec(_ context.Context, _ string, _ runtime.ExecOpts) (runtime.Process, error) {
 	return nil, fmt.Errorf("cannot exec in a paused state")
 }
 
-func (s *pausedState) Status(ctx context.Context) (string, error) {
+func (s *pausedState) Status(_ context.Context) (string, error) {
 	return "paused", nil
 }
 
@@ -257,23 +257,23 @@ func (s *stoppedState) transition(name string) error {
 	return nil
 }
 
-func (s *stoppedState) Pause(ctx context.Context) error {
+func (s *stoppedState) Pause(_ context.Context) error {
 	return fmt.Errorf("cannot pause a stopped container")
 }
 
-func (s *stoppedState) Resume(ctx context.Context) error {
+func (s *stoppedState) Resume(_ context.Context) error {
 	return fmt.Errorf("cannot resume a stopped container")
 }
 
-func (s *stoppedState) Update(ctx context.Context, r *google_protobuf.Any) error {
+func (s *stoppedState) Update(_ context.Context, _ *google_protobuf.Any) error {
 	return fmt.Errorf("cannot update a stopped container")
 }
 
-func (s *stoppedState) Checkpoint(ctx context.Context, r *CheckpointConfig) error {
+func (s *stoppedState) Checkpoint(_ context.Context, _ *CheckpointConfig) error {
 	return fmt.Errorf("cannot checkpoint a stopped container")
 }
 
-func (s *stoppedState) Start(ctx context.Context) error {
+func (s *stoppedState) Start(_ context.Context) error {
 	return fmt.Errorf("cannot start a stopped process")
 }
 
@@ -288,15 +288,15 @@ func (s *stoppedState) Kill(ctx context.Context, sig uint32, all bool) error {
 	return s.p.kill(ctx, sig, all)
 }
 
-func (s *stoppedState) SetExited(status int) {
+func (s *stoppedState) SetExited(_ int) {
 	// no op
 }
 
-func (s *stoppedState) Exec(ctx context.Context, id string, opts runtime.ExecOpts) (runtime.Process, error) {
+func (s *stoppedState) Exec(_ context.Context, _ string, _ runtime.ExecOpts) (runtime.Process, error) {
 	return nil, fmt.Errorf("cannot exec in a stopped state")
 }
 
-func (s *stoppedState) Status(ctx context.Context) (string, error) {
+func (s *stoppedState) Status(_ context.Context) (string, error) {
 	return "stopped", nil
 }
 
diff --git a/io.go b/io.go
index f6b6b50..c795480 100644
--- a/io.go
+++ b/io.go
@@ -176,7 +176,7 @@ func (p *processIO) CopyStdin() error {
 	return nil
 }
 
-func createIO(ctx context.Context, id string, ioUID, ioGID int, stdio stdio.Stdio) (*processIO, error) {
+func createIO(_ context.Context, _ string, ioUID, ioGID int, stdio stdio.Stdio) (*processIO, error) {
 	pio := &processIO{
 		stdio: stdio,
 	}
@@ -289,7 +289,7 @@ func withConditionalIO(c stdio.Stdio) runc.IOOpt {
 	}
 }
 
-func openRWFifo(ctx context.Context, fn string, perm os.FileMode) (*os.File, error) {
+func openRWFifo(_ context.Context, fn string, perm os.FileMode) (*os.File, error) {
 	if _, err := os.Stat(fn); err != nil {
 		if os.IsNotExist(err) {
 			if err := syscall.Mkfifo(fn, uint32(perm&os.ModePerm)); err != nil && !os.IsExist(err) {
diff --git a/platform.go b/platform.go
index 28020da..8990d15 100644
--- a/platform.go
+++ b/platform.go
@@ -45,7 +45,7 @@ type linuxPlatform struct {
 	epoller *console.Epoller
 }
 
-func (p *linuxPlatform) CopyConsole(ctx context.Context, console console.Console, id, stdin, stdout, stderr string, wg *sync.WaitGroup) (cons console.Console, retErr error) {
+func (p *linuxPlatform) CopyConsole(ctx context.Context, console console.Console, _, stdin, stdout, _ string, wg *sync.WaitGroup) (cons console.Console, retErr error) {
 	if p.epoller == nil {
 		return nil, fmt.Errorf("uninitialized epoller")
 	}
@@ -95,7 +95,7 @@ func (p *linuxPlatform) CopyConsole(ctx context.Context, console console.Console
 	return epollConsole, nil
 }
 
-func (p *linuxPlatform) ShutdownConsole(ctx context.Context, cons console.Console) error {
+func (p *linuxPlatform) ShutdownConsole(_ context.Context, cons console.Console) error {
 	if p.epoller == nil {
 		return fmt.Errorf("uninitialized epoller")
 	}
diff --git a/reload.go b/reload.go
index 84cc660..261a56d 100644
--- a/reload.go
+++ b/reload.go
@@ -88,7 +88,7 @@ func (manager *TaskManager) loadTasks(ctx context.Context) error {
 	return nil
 }
 
-func (manager *TaskManager) loadShim(ctx context.Context, bundle *pkgbundle.Bundle) (_ *shim, retErr error) {
+func (manager *TaskManager) loadShim(_ context.Context, bundle *pkgbundle.Bundle) (_ *shim, retErr error) {
 	init, err := renewInitProcess(bundle)
 	if err != nil {
 		return nil, err
diff --git a/shim.go b/shim.go
index f6898db..cb0a366 100644
--- a/shim.go
+++ b/shim.go
@@ -135,11 +135,11 @@ func (s *shim) Namespace() string {
 	return s.bundle.Namespace
 }
 
-func (s *shim) Pause(ctx context.Context) error {
+func (s *shim) Pause(_ context.Context) error {
 	return fmt.Errorf("pause not implemented yet")
 }
 
-func (s *shim) Resume(ctx context.Context) error {
+func (s *shim) Resume(_ context.Context) error {
 	return fmt.Errorf("resume not implemented yet")
 }
 
@@ -173,20 +173,20 @@ func (s *shim) Exec(ctx context.Context, execID string, opts runtime.ExecOpts) (
 	return process, nil
 }
 
-func (s *shim) Pids(ctx context.Context) ([]runtime.ProcessInfo, error) {
+func (s *shim) Pids(_ context.Context) ([]runtime.ProcessInfo, error) {
 	return []runtime.ProcessInfo{
 		{Pid: s.PID()},
 	}, nil
 }
 
-func (s *shim) ResizePty(ctx context.Context, size runtime.ConsoleSize) error {
+func (s *shim) ResizePty(_ context.Context, size runtime.ConsoleSize) error {
 	return s.init.Resize(console.WinSize{
 		Width:  uint16(size.Width),
 		Height: uint16(size.Height),
 	})
 }
 
-func (s *shim) CloseIO(ctx context.Context) error {
+func (s *shim) CloseIO(_ context.Context) error {
 	if stdin := s.init.Stdin(); stdin != nil {
 		if err := stdin.Close(); err != nil {
 			return err
@@ -195,7 +195,7 @@ func (s *shim) CloseIO(ctx context.Context) error {
 	return nil
 }
 
-func (s *shim) Wait(ctx context.Context) (*runtime.Exit, error) {
+func (s *shim) Wait(_ context.Context) (*runtime.Exit, error) {
 	taskPid := s.PID()
 
 	// TODO: use ctx
@@ -208,7 +208,7 @@ func (s *shim) Wait(ctx context.Context) (*runtime.Exit, error) {
 	}, nil
 }
 
-func (s *shim) Checkpoint(ctx context.Context, path string, options *ptypes.Any) error {
+func (s *shim) Checkpoint(_ context.Context, _ string, _ *ptypes.Any) error {
 	return fmt.Errorf("checkpoint not implemented yet")
 }
 
@@ -220,7 +220,7 @@ func (s *shim) Update(ctx context.Context, resources *ptypes.Any, _ map[string]s
 	return s.init.Update(ctx, resources)
 }
 
-func (s *shim) Stats(ctx context.Context) (*ptypes.Any, error) {
+func (s *shim) Stats(_ context.Context) (*ptypes.Any, error) {
 	cgx := s.cg
 	if cgx == nil {
 		return nil, fmt.Errorf("cgroup does not exist: %w", errdefs.ErrNotFound)