anchor.diff:  -export([ init/1
           , handle_call/3
           , handle_cast/2
  +        , handle_info/2
  +        , terminate/2
  +        , code_change/3
           ]).
   
   -type state() :: #{ count   => integer()
  
positive.code:            },
    {ok, State}.
  
  -spec handle_call(any(), any(), state()) -> {noreply, state()}.
  handle_call( await
             , From
  
negative.code: %% gen_server callbacks
  %%------------------------------------------------------------------------------
  
  %% @private
  -spec init(any()) -> {ok, state()}.
  init(N) ->
    State = #{ count   => N
  