It's not possible to connect to a running mongod instance on a Mac.
Even the provided test example fails with the following message:
— FAIL: TestDocumentationExamples (0.00s)
        Error Trace:    examples.go:60
                        examples_test.go:26
        Error:          Received unexpected error:
                        topology is closed
FAIL
FAIL    command-line-arguments  0.014s