Go 1.5 で PKCS8 秘密キーをマーシャルするにはどうすればよいですか?

<code class="go">import (
    "crypto/rsa"
    "crypto/asn1"
    "crypto/x509"
)

type pkcs8Key struct {
    Version             int
    PrivateKeyAlgorithm []asn1.ObjectIdentifier
    PrivateKey          []byte
}


func rsa2pkcs8(key *rsa.PrivateKey) ([]byte, error) {
    var pkey pkcs8Key
    pkey.Version = 0
    pkey.PrivateKeyAlgorithm = make([]asn1.ObjectIdentifier, 1)
    pkey.PrivateKeyAlgorithm[0] = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 1}
    pkey.PrivateKey = x509.MarshalPKCS1PrivateKey(key)

    return asn1.Marshal(pkey)
}</code>