Took some time, but I think I put the pieces together – I hope they stay together 
With that widgets are working in my Go kernel:
For others similarly looking for how to make front-end connect to kernel/users’s cell program:
- Detailed communication documentation for the GoNB kernel – one could apply the same ideas for other languages/kernels.
- Javascript code used to connect to the kernel, which could also be reused for other kernels – I’m a noob javascript coder, but it seems to work.