Evaluate nil values from gomobile bind

What's the right way to evaluate nil returned values from Go functions in Android Java?

Here's what I've tried:

// ExportedGoFunction returns a pointer to a GoStruct or nil in case of fail
func ExportedGoFunction() *GoStruct {
  return nil
}

Then I generate a .aar file via gomobile using:

gomobile bind -v --target=android

In my Java code I tried to evaluate nil as null but it's not working. Java Code:

GoLibrary.GoStruct goStruct = GoLibrary.ExportedGoFunction();
if (goStruct != null) {
   // This block should not be executed, but it is
   Log.d("GoLog", "goStruct is not null");
}

Disclaimer: Other methods from the go library work flawless

For possible future reference, as of 09/2015 I've come up with two ways of dealing with the problem.

The first one is to return an error from the Go code and try/catch-ing the error in Java. Here's an example:

// ExportedGoFunction returns a pointer to a GoStruct or nil in case of fail
func ExportedGoFunction() (*GoStruct, error) {
   result := myUnexportedGoStruct()
   if result == nil {
      return nil, errors.New("Error: GoStruct is Nil")
   }

   return result, nil
}

And then try/catch the error in Java

try {
   GoLibrary.GoStruct myStruct = GoLibrary.ExportedGoFunction();
} 
catch (Exception e) {
   e.printStackTrace(); // myStruct is nil   
}

This approach is both idiomatic Go and Java, but even if it works on preventing the program to crash, it ends up bloating the code with try/catch statements and causing yet more overhead.

So, based on user @SnoProblem answers the non-idiomatic way of solving it and properly handle null values I came up with was:

// NullGoStruct returns false if value is nil or true otherwise
func NullGoStruct(value *GoStruct) bool {
    return (value == nil) 
}

And then check the code in Java like:

GoLibrary.GoStruct value = GoLibrary.ExportedGoFunction();
if (GoLibrary.NullGoStruct(value)) {
   // This block is executed only if value has nil value in Go
   Log.d("GoLog", "value is null");
}

1: https://stackoverflow.com/users/4638952/snoproblem "@SnoProblem"

Looking through the testing package for go mobile, it looks like you need to cast the null value to the type.

From the SeqTest.java file:

 public void testNilErr() throws Exception {
    Testpkg.Err(null); // returns nil, no exception
  }

Edit: A non-exception example, too:

byte[] got = Testpkg.BytesAppend(null, null);
assertEquals("Bytes(null+null) should match", (byte[])null, got);
got = Testpkg.BytesAppend(new byte[0], new byte[0]);
assertEquals("Bytes(empty+empty) should match", (byte[])null, got);

It may be as simple as:

GoLibrary.GoStruct goStruct = GoLibrary.ExportedGoFunction();
if (goStruct != (GoLibrary.GoStruct)null) {
   // This block should not be executed, but it is
   Log.d("GoLog", "goStruct is not null");
}

EDIT: Suggestion for utility method:

You could add a utility function to the library to give you the typed nil value.

func NullVal() *GoStruct {
    return nil
}

Still a bit hacky, but it should be less overhead than multiple wrappers and exception handling.