can't send signals

Signals do not work, at least on OSX with goon:

iex(3)> proc = Porcelain.spawn("sleep", ["30"], [])
%Porcelain.Process{err: nil, out: :string, pid: #PID<0.153.0>}
iex(4)> Porcelain.Process.signal proc, 15
{:signal, 15}
iex(5)> Porcelain.Process.signal proc, :kill
{:signal, :kill}
iex(6)>

I still keep seeing the process:

$ ps axww | fgrep sleep
48681 ?? Ss 0:00.01 /usr/local/bin/goon -proto 2.0 -out -- /bin/sleep 30
48682 ?? S 0:00.00 /bin/sleep 30
48690 s007 S+ 0:00.00 fgrep sleep