(Go) RSA SHA256 Signature using Private Key from Java Keystore

Signs plaintext using RSA SHA256 using a key from a Java keystore.

Duplicatest this code:

KeyStore keystore; // key repository for keys containing signature certificate
String alias; // alias for the certificate in the key repository
String password; // password for the certificate's private key
String plaintext; // text being signed


Signature signature = Signature.getInstance("SHA256withRSA");
signature.initSign((PrivateKey) keystore.getKey(alias, password.toCharArray()));
signature.update(plaintext.getBytes("UTF-8"));
byte[] rsa_text= signature.sign();

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

    jks := chilkat.NewJavaKeyStore()

    jksPassword := "secret"

    // Load the Java keystore from a file.  The JKS file password is used
    // to verify the keyed digest that is found at the very end of the keystore.
    // It verifies that the keystore has not been modified.
    success := jks.LoadFile(jksPassword,"qa_data/jks/sample_secret.jks")
    if success != true {
        fmt.Println(jks.LastErrorText())
        jks.DisposeJavaKeyStore()
        return
    }

    // Get the private key from the JKS.
    // The private key password may be different than the file password.
    privKeyPassword := "secret"
    caseSensitive := false
    privKey := jks.FindPrivateKey(privKeyPassword,"some.alias",caseSensitive)
    if jks.LastMethodSuccess() != true {
        fmt.Println(jks.LastErrorText())
        jks.DisposeJavaKeyStore()
        return
    }

    // Establish the RSA object and tell it to use the private key..
    rsa := chilkat.NewRsa()

    success = rsa.ImportPrivateKeyObj(privKey)
    privKey.DisposePrivateKey()
    if success != true {
        fmt.Println(rsa.LastErrorText())
        jks.DisposeJavaKeyStore()
        rsa.DisposeRsa()
        return
    }

    // Indicate we'll be signing the utf-8 byte representation of the string..
    rsa.SetCharset("utf-8")

    // Sign some plaintext using RSA-SHA256
    var binarySignature []byte
    plaintext := "this is the text to be signed"
    binarySignature = rsa.SignString(plaintext,"SHA256")
    if rsa.LastMethodSuccess() != true {
        fmt.Println(rsa.LastErrorText())
        jks.DisposeJavaKeyStore()
        rsa.DisposeRsa()
        return
    }

    // Alternatively, if the signature is desired in some encoded string form,
    // such as base64, base64-url, hex, etc.
    rsa.SetEncodingMode("base64-url")
    signatureStr := rsa.SignStringENC(plaintext,"SHA256")
    fmt.Println("base64-url RSA signature: ", *signatureStr)

    jks.DisposeJavaKeyStore()
    rsa.DisposeRsa()