How should we parse BinarySecurityToken？

Question

Our MDM server received an enrollment request from the client. We got BinarySecurityToken and tried to parse it, but it always went wrong. How do I resolve BinarySecurityToken?
We did it in the following way
certificateSigningRequestDer, err := base64.StdEncoding.DecodeString(binarySecurityToken)
if err != nil {
return nil, err
}
// Decode and verify CSR
csr, err := x509.ParseCertificateRequest(certificateSigningRequestDer)
if err != nil {
panic(err)
}

enrollment-protocol.txt has detailed data

Can you help us resolve this parsing error?[enter code here][1]