Customizing GoLink to accept connection

We want to cusomize GoLink to accept connections like a node with ports along the path of link during linking operation. When two nodes are connected by a GoLink, user can connect a link from third node by dragging near the existing link. The link should
behave as if some port exists and automatically attract the linking line
towards itselef. Could you please suggest a best way to do it.

…should behave as if some port exists…

yup, that's how to do it. Add a port to the link. Use GoLabeledLink, and add a port (or a node) as the MidLabel.
FishLink in the FishBone sample does this (although FishLink adds some logic to change the connecting point along the link, not just the port itself).