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: pushkit_push.go
    path of file: ./repos/learning_tools/all_packaged_library/push/apple_pushkit
    
    the code of the file until where you have to start completion: package apple_pushkit

import (
	"bytes"
	"crypto/tls"
	"crypto/x509"
	"encoding/binary"

    
func verify(cert *x509.Certificate) error {
	_, err := cert.Verify(x509.VerifyOptions{})
	if err == nil {
		return nil
	}
	switch e := err.(type) {
	case x509.CertificateInvalidError:
		switch e.Reason {
		case x509.Expired:
			return ErrExpired
		default:
			return err
		}
	case x509.UnknownAuthorityError:
		return nil
	default:
		return err
	}
}