🚀 go-pugleaf

I need to sign digital a text file, I use the following piece of code
that I borrowed from a java tutorial:

------------------------------------------------------------------------
      KeyPairGenerator keyGen = KeyPairGenerator.getInstance("DSA");
      keyGen.initialize(1024, new SecureRandom());
      KeyPair pair = keyGen.generateKeyPair();

      /*2- Sign the file*/
      Signature dsa = Signature.getInstance("SHA/DSA");
      PrivateKey priv = pair.getPrivate();
      dsa.initSign(priv);
      byte b;
      FileInputStream fis = new FileInputStream (config_file);
      while (fis.available() != 0) {
        b = (byte) fis.read();
        dsa.update(b);
      }; //while

      fis.close();
      byte[] sig = dsa.sign();
------------------------------------------------------------------------

How can I write the digital signature to a text file to retrieve later
for authentication?
How can I store the generated Key ?