I have my shotty with a Magpul MS3 sling, that sling can be used as 2 point or 1 point sling, and has a quick detach.
1 point sling is useful to free your hands to do quick tasks.
2 point is better for long walks where no contact is expected.
No sling is better for combat, upon contact I would hit the quick detach, that way you can move around better, shoot from the left side etc.
I know, if I need to transition to secondary I might lose the shotgun, but who cares, at the moment I need to transition, my shotgun isn't solving my current problem.
BTW: My primary is a shotgun because in Argentina we already have an "assault weapons" ban since '94.