Postgres replication globally
I'm sorry, but IT isn't magic...
If your network has high latency how can you expect data change to be spread without latency ?

But if you don't care about your writing rate on the master, you can slow it down with synchronous replication and you won't have any latency between your master and your standby. Of course you will now face writing lag on your master!

I'm afraid postgreSQL isn't suitable for your need in that case... 
Here, you're facing the CAP theorem issue. Maybe, you could try another approach to favor consistency and partition tolerance as MongoDB, BigTable or Redis ?