Clearing Postman DNS cache

Postman apparently defers to the underlying OS for DNS lookup cache.

Hence in order to clear Postman DNS cache, we need to clear the underlying OS's cache.

This can be done on MacOS:

sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

Ref: https://mackeeper.com/blog/flush-dns-cache-on-mac/