(Go) Duplicate OpensSSL to Sign File and Output Binary DER

This example duplicates the following:

openssl smime -sign -in INPUT.xml -signer SIGN.PEM -passin pass:MYPASS -outform der -binary -nodetach -out SIGNED.P7M

Note: Although "smime" is the OpenSSL command, it's not actually producing S/MIME. The arguments "-outform der -binary" indicates that the output is binary DER (i.e. the PKCS7 binary signature). The input can be any type of file: XML, PDF, JPG, ... *anything*...

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    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    crypt := chilkat.NewCrypt2()

    // Load the PEM containing cert + private key.
    pem := chilkat.NewPem()
    success := pem.LoadPemFile("qa_data/pem/myPem.pem","password")
    if success != true {
        fmt.Println(pem.LastErrorText())
        return
    }

    privkey := pem.GetPrivateKey(0)
    if pem.LastMethodSuccess() != true {
        fmt.Println(pem.LastErrorText())
        return
    }

    cert := pem.GetCert(0)
    if pem.LastMethodSuccess() != true {
        privkey.DisposePrivateKey()
        fmt.Println(pem.LastErrorText())
        return
    }

    success = crypt.SetSigningCert2(cert,privkey)
    if success != true {
        privkey.DisposePrivateKey()
        cert.DisposeCert()
        fmt.Println(crypt.LastErrorText())
        return
    }

    privkey.DisposePrivateKey()
    cert.DisposeCert()

    // Alternatively, we could use a .pfx/.p12 file.
    // (Chilkat also supports other formats/sources for cert/private keys...)
    certFromP12 := chilkat.NewCert()
    success = certFromP12.LoadPfxFile("qa_data/p12/myP12.p12","password")
    if success != true {
        fmt.Println(certFromP12.LastErrorText())
        return
    }

    // The certificate, when loaded from a .pfx/.p12, will automatically 
    // include the associated private key, assuming it's present in the .p12.
    // We don't have to explicitly provide the private key as in the
    // lines of code above that use the PEM file.
    success = crypt.SetSigningCert(certFromP12)
    if success != true {
        fmt.Println(crypt.LastErrorText())
        return
    }

    // Create the opaque signature (PKCS7 binary DER that contains both the signature and original file data).
    success = crypt.CreateP7M("qa_data/infile.anything","qa_output/outfile.p7m")
    if success != true {
        fmt.Println(crypt.LastErrorText())
        return
    }

    fmt.Println("Success.")