Checking order of operations for async call within sync call

check_order.erl

-module(check_order).
-behaviour(gen_server).
-export([
    start_link/0,
    thing/1,

    init/1,
    handle_call/3,
    handle_cast/2
]).

-record(state, {text :: string()}).

start_link() ->
    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).

thing(Pid) ->
    gen_server:call(Pid, thing).

async_thing(Pid) ->
    gen_server:cast(Pid, async_thing).

init(_Args) ->
    {ok, #state{text = "init"}}.

handle_call(thing, _From, _State = #state{text = CurrentText}) ->
    io:format("Starting async thing...~n"),
    async_thing(self()),
    io:format("Sleep 1 second...~n"),
    ok = timer:sleep(1000),
    {reply, {thing, CurrentText}, #state{text = "async_thing"}}.

handle_cast(async_thing, State = #state{text = CurrentText}) ->
    io:format("Async thing says ~p...~n", [CurrentText]),
    {noreply, State}.

shell

rebar3 shell
===> Verifying dependencies...
===> Analyzing applications...
===> Compiling reminder
Erlang/OTP 25 [erts-13.2.2] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [jit]

Eshell V13.2.2  (abort with ^G)
1> {ok, Pid} = check_order:start_link().
{ok,<0.162.0>}
2> check_order:thing(Pid).
Starting async thing...
Sleep 1 second...
Async thing says "async_thing"...
{thing,"init"}