You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: reconciler.go
    path of file: ./repos/gardener/pkg/resourcemanager/controller/garbagecollector
    
    the code of the file until where you have to start completion: // Copyright 2021 SAP SE or an SAP affiliate company. All rights reserved. This file is licensed under the Apache Software License, v. 2 except as noted otherwise in the LICENSE file
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package garbagecollector

import (
	"context"
	"time"

	"github.com/hashicorp/go-multierror"
	appsv1 "k8s.io/api/apps/v1"
	batchv1 "k8s.io/api/batch/v1"
	corev1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/api/meta"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/apimachinery/pkg/util/wait"
	"k8s.io/utils/clock"
	"sigs.k8s.io/controller-runtime/pkg/client"
	logf "sigs.k8s.io/controller-runtime/pkg/log"
	"sigs.k8s.io/controller-runtime/pkg/reconcile"

	resourcesv1alpha1 "github.com/gardener/gardener/pkg/apis/resources/v1alpha1"
	"github.com/gardener/gardener/pkg/controllerutils"
	"github.com/gardener/gardener/pkg/resourcemanager/apis/config"
	"github.com/gardener/gardener/pkg/resourcemanager/controller/garbagecollector/references"
	errorsutils "github.com/gardener/gardener/pkg/utils/errors"
)

// Reconciler performs garbage collection.
type Reconciler struct {
	TargetReader          client.Reader
	TargetWriter          client.Writer
	Config                config.GarbageCollectorControllerConfig
	Clock                 clock.Clock
	MinimumObjectLifetime *time.Duration
}

// Reconcile performs the main reconciliation logic.
func (r *Reconciler) Reconcile(reconcileCtx context.Context, _ reconcile.Request) (reconcile.Result, error) {
	log := logf.FromContext(reconcileCtx)

	ctx, cancel := controllerutils.GetMainReconciliationContext(reconcileCtx, r.Config.SyncPeriod.Duration)
	defer cancel()

	log.Info("Starting garbage collection")
	defer log.Info("Garbage collection finished")

	var (
		labels                  = client.MatchingLabels{references.LabelKeyGarbageCollectable: references.LabelValueGarb
    
func (r *Reconciler) Reconcile(reconcileCtx context.Context, _ reconcile.Request) (reconcile.Result, error) {
	log := logf.FromContext(reconcileCtx)

	ctx, cancel := controllerutils.GetMainReconciliationContext(reconcileCtx, r.Config.SyncPeriod.Duration)
	defer cancel()

	log.Info("Starting garbage collection")
	defer log.Info("Garbage collection finished")

	var (
		labels                  = client.MatchingLabels{references.LabelKeyGarbageCollectable: references.LabelValueGarbageCollectable}
		objectsToGarbageCollect = map[objectId]struct{}{}
	)

	for _, resource := range []struct {
		kind     string
		listKind string
	}{
		{references.KindSecret, "SecretList"},
		{references.KindConfigMap, "ConfigMapList"},
	} {
		objList := &metav1.PartialObjectMetadataList{}
		objList.SetGroupVersionKind(corev1.SchemeGroupVersion.WithKind(resource.listKind))
		if err := r.TargetReader.List(ctx, objList, labels); err != nil {
			return reconcile.Result{}, err
		}

		for _, obj := range objList.Items {
			if obj.CreationTimestamp.Add(*r.MinimumObjectLifetime).UTC().After(r.Clock.Now().UTC()) {
				// Do not consider recently created objects for garbage collection.
				continue
			}

			objectsToGarbageCollect[objectId{resource.kind, obj.Namespace, obj.Name}] = struct{}{}
		}
	}

	var (
		items             []metav1.PartialObjectMetadata
		groupVersionKinds = []schema.GroupVersionKind{
			appsv1.SchemeGroupVersion.WithKind("DeploymentList"),
			appsv1.SchemeGroupVersion.WithKind("StatefulSetList"),
			appsv1.SchemeGroupVersion.WithKind("DaemonSetList"),
			batchv1.SchemeGroupVersion.WithKind("JobList"),
			corev1.SchemeGroupVersion.WithKind("PodList"),
			batchv1.SchemeGroupVersion.WithKind("CronJobList"),
			resourcesv1alpha1.SchemeGroupVersion.WithKind("ManagedResourceList"),
		}
	)

	for _, gvk := range groupVersionKinds {
		objList := &metav1.PartialObjectMetadataList{}
		objList.SetGroupVersionKind(gvk)
		if err := r.TargetReader.List(ctx, objList); err != nil {
			if !meta.IsNoMatchError(err) {
				return reconcile.Result{}, err
			}
		}
		items = append(items, objList.Items...)
	}

	for _, objectMeta := range items {
		for key, objectName := range objectMeta.Annotations {
			objectKind := references.KindFromAnnotationKey(key)
			if objectKind == "" || objectName == "" {
				continue
			}

			delete(objectsToGarbageCollect, objectId{objectKind, objectMeta.Namespace, objectName})
		}
	}

	var (
		results   = make(chan error, 1)
		wg        wait.Group
		errorList = &multierror.Error{ErrorFormat: errorsutils.NewErrorFormatFuncWithPrefix("Could not delete all unused resources")}
	)

	for id := range objectsToGarbageCollect {
		objId := id
		wg.StartWithContext(ctx, func(ctx context.Context) {
			var (
				meta = metav1.ObjectMeta{Namespace: objId.namespace, Name: objId.name}
				obj  client.Object
			)

			switch objId.kind {
			case references.KindSecret:
				obj = &corev1.Secret{ObjectMeta: meta}
			case references.KindConfigMap:
				obj = &corev1.ConfigMap{ObjectMeta: meta}
			default:
				return
			}

			log.Info("Delete resource",
				"kind", objId.kind,
				"namespace", objId.namespace,
				"name", objId.name,
			)

			if err := r.TargetWriter.Delete(ctx, obj); client.IgnoreNotFound(err) != nil {
				results <- err
			}
		})
	}

	go func() {
		wg.Wait()
		close(results)
	}()

	for err := range results {
		if err != nil {
			errorList = multierror.Append(errorList, err)
		}
	}

	return reconcile.Result{Requeue: true, RequeueAfter: r.Config.SyncPeriod.Duration}, errorList.ErrorOrNil()
}