AFAIK- HAProxy can only append an x-forwarded-for in layer 7 mode (http). Unfortunately, using HAProxy for PostgreSQL connections is layer 4 (tcp). The best you could do would be to route the connection through something like pgbouncer and have it append the source IP in the app name.
We have setup in Postgres HA Cluster using Patroni. Also we have used the HAProxy for load balancing...
On Postgres side, we are getting HaProxy IP instead of Client IP, while checking in pg_stat_activity tables. Can you please suggest the changes needs to be done on HAProxy or Postgres side?
Postgresql does not know that HAProxy is a proxy. It just knows that an IP address (which just happens to come from an HAProxy server) has connected and "doing stuff".