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: csr.go
    path of file: ./repos/kubernetes/staging/src/k8s.io/client-go/util/certificate/csr
    
    the code of the file until where you have to start completion: /*
Copyright 2016 The Kubernetes Authors.

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 csr

import (
	"context"
	"crypto"
	"crypto/x509"
	"encoding/pem"
	"fmt"
	"reflect"
	"time"

	certificatesv1 "k8s.io/api/certificates/v1"
	certificatesv1beta1 "k8s.io/api/certificates/v1beta1"
	apierrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/fields"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/apim
    
func RequestCertificate(client clientset.Interface, csrData []byte, name, signerName string, requestedDuration *time.Duration, usages []certificatesv1.KeyUsage, privateKey interface{}) (reqName string, reqUID types.UID, err error) {
	csr := &certificatesv1.CertificateSigningRequest{
		// Username, UID, Groups will be injected by API server.
		TypeMeta: metav1.TypeMeta{Kind: "CertificateSigningRequest"},
		ObjectMeta: metav1.ObjectMeta{
			Name: name,
		},
		Spec: certificatesv1.CertificateSigningRequestSpec{
			Request:    csrData,
			Usages:     usages,
			SignerName: signerName,
		},
	}
	if len(csr.Name) == 0 {
		csr.GenerateName = "csr-"
	}
	if requestedDuration != nil {
		csr.Spec.ExpirationSeconds = DurationToExpirationSeconds(*requestedDuration)
	}

	reqName, reqUID, err = create(client, csr)
	switch {
	case err == nil:
		return reqName, reqUID, err

	case apierrors.IsAlreadyExists(err) && len(name) > 0:
		klog.Infof("csr for this node already exists, reusing")
		req, err := get(client, name)
		if err != nil {
			return "", "", formatError("cannot retrieve certificate signing request: %v", err)
		}
		if err := ensureCompatible(req, csr, privateKey); err != nil {
			return "", "", fmt.Errorf("retrieved csr is not compatible: %v", err)
		}
		klog.Infof("csr for this node is still valid")
		return req.Name, req.UID, nil

	default:
		return "", "", formatError("cannot create certificate signing request: %v", err)
	}
}