(get-header resp header-name)
Looks up a header in a Ring response (or request) case insensitively,
returning the value of the header, or nil if not present.
Source
(defn get-header
"Looks up a header in a Ring response (or request) case insensitively,
returning the value of the header, or nil if not present."
{:added "1.2"}
[resp header-name]
(some-> resp (find-header header-name) val))