Use singleton in various classes

src/handlers/log_handler.cr

@@ -2,20 +2,17 @@ require "kemal"
 require "../logger"
 
 class LogHandler < Kemal::BaseLogHandler
-  def initialize(@logger : Logger)
-  end
-
   def call(env)
     elapsed_time = Time.measure { call_next env }
     elapsed_text = elapsed_text elapsed_time
     msg = "#{env.response.status_code} #{env.request.method}" \
           " #{env.request.resource} #{elapsed_text}"
-    @logger.debug msg
+    Logger.debug msg
     env
   end
 
   def write(msg)
-    @logger.debug msg
+    Logger.debug msg
   end
 
   private def elapsed_text(elapsed)