01 Proc.in.close hang.p6

my $proc = run «cat -», :in, :out, :bin;
say "started";

my $input = ("a" x 1000000).encode;
say "input encoded";

my $promise = start {
    $proc.in.write: $input;
    say "input written";

    $proc.in.close;
    say "input closed";
}

say $proc.out.slurp-rest(:close, :bin).bytes;
say "output read";

await $promise;
say "all done";

02 output

started
input encoded
input written