some basic pem decode ways using the crypto interface

pem_decode_crypto.go

func decodeBackToPEMWithName(fname string, pk crypto.PrivateKey) string {
	pemPrivateFile, _ := os.Create(fname)
	var pemPrivateBlock = &pem.Block{
		Type:  "RSA PRIVATE KEY",
		Bytes: x509.MarshalPKCS1PrivateKey(pk.(*rsa.PrivateKey)),
	}

	pem.Encode(pemPrivateFile, pemPrivateBlock)
	pemPrivateFile.Close()
	return string(pemPrivateBlock.Bytes)
}

func decodeBackToPEM(pk crypto.PrivateKey) string {
	pemPrivateFile, _ := os.Create("DecryptBytes_priv.key")
	var pemPrivateBlock = &pem.Block{
		Type:  "RSA PRIVATE KEY",
		Bytes: x509.MarshalPKCS1PrivateKey(pk.(*rsa.PrivateKey)),
	}

	pem.Encode(pemPrivateFile, pemPrivateBlock)
	pemPrivateFile.Close()
	return string(pemPrivateBlock.Bytes)
}