Add memoization to lazy param parsing

src/kemal/context.cr

@@ -2,7 +2,6 @@
 # information such as params, content_type e.g
 class HTTP::Server
   class Context
-
     def params
       @request.url_params = route_lookup.params
       @params ||= Kemal::ParamParser.new(@request)

src/kemal/param_parser.cr

@@ -18,7 +18,12 @@ class Kemal::ParamParser
 
   {% for method in %w(url query body json) %}
   def {{method.id}}
+    # check memoization
+    return @{{method.id}} if @{{method.id}}_parsed
+
     parse_{{method.id}}
+    # memoize
+    @{{method.id}}_parsed = true
     @{{method.id}}
   end
   {% end %}
@@ -67,6 +72,4 @@ class Kemal::ParamParser
     end
     part_params
   end
-
 end
-