GoBGP not generating Path-ID automatically for vpnv4 routes even after enabling add-path send capability

[AnanthNantha]

I have enabled add-path send capability for my BGP peer. I am adding two vpnv4 routes.

[user@test]# gobgp global rib -a vpnv4 add 22.22.22.22/32 label 100 rd 55:1 origin igp aspath 7777,8888 nexthop 111.0.0.1 rt 55:1
[user@test]# gobgp global rib -a vpnv4
Network Labels Next Hop AS_PATH Age Attrs
*> 55:1:22.22.22.22/32 [100] 111.0.0.1 7777 8888 00:00:05 [{Origin: i} {Extcomms: [55:1]}]

Then I am adding an another route with same prefix, but different AS-path and nexthop.
[user@test]# gobgp global rib -a vpnv4 add 22.22.22.22/32 label 100 rd 55:1 origin igp aspath 1,2 nexthop 112.0.0.2 rt 55:1
[user@test]# gobgp global rib -a vpnv4
Network Labels Next Hop AS_PATH Age Attrs
*> 55:1:22.22.22.22/32 [100] 112.0.0.2 1 2 00:00:04 [{Origin: i} {Extcomms: [55:1]}]

While adding the second route, it is overwriting the previous route.

I tried adding identifier option. But looks like it is available/working only for ipv4 address family. It is not working for vpnv4. But anyway irrespective of the identifier, gobgp should generate PATH-ID itself right? I mean I don't remember configuring any path-identifier manually in Junos devices.

Please let me know if I am missing something here.