(Go) Duplicate openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

Demonstrates how to duplicate this OpenSSL command:

openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

1. Creates a SHA256 digest of the contents of the input file.
2. Verifies the SHA256 digest using the public key.

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

    pubKey := chilkat.NewPublicKey()

    // Load the public key from an PEM file:
    success := pubKey.LoadFromFile("pubKey.pem")
    if success != true {
        fmt.Println(pubKey.LastErrorText())
        pubKey.DisposePublicKey()
        return
    }

    // Load the data of the original file that was signed.
    bdFileData := chilkat.NewBinData()
    success = bdFileData.LoadFile("in.dat")

    // Load the signature.
    bdSig := chilkat.NewBinData()
    success = bdSig.LoadFile("signature.sig")

    rsa := chilkat.NewRsa()

    // Import the public key into the RSA component:
    success = rsa.ImportPublicKeyObj(pubKey)
    if success != true {
        fmt.Println(rsa.LastErrorText())
        pubKey.DisposePublicKey()
        bdFileData.DisposeBinData()
        bdSig.DisposeBinData()
        rsa.DisposeRsa()
        return
    }

    // OpenSSL uses big-endian.
    rsa.SetLittleEndian(false)

    success = rsa.VerifyBd(bdFileData,"sha256",bdSig)
    if success != true {
        fmt.Println(rsa.LastErrorText())
        fmt.Println("The signature was invalid.")
        pubKey.DisposePublicKey()
        bdFileData.DisposeBinData()
        bdSig.DisposeBinData()
        rsa.DisposeRsa()
        return
    }

    fmt.Println("The signature was verified.")

    pubKey.DisposePublicKey()
    bdFileData.DisposeBinData()
    bdSig.DisposeBinData()
    rsa.DisposeRsa()