feat(Poolboy): ensure Poolboy waits infinitely for a worker

To prevent Poolboy from timing out whilst waiting for a worker, the
`:infinity` atom is passed as the `TIMEOUT` argument in the Poolboy
transaction function call. This will ensure Poolboy waits forever for a
worker to become available.

To highlight the issue more, a sleep has been added to the worker to
simulate slow running processes.

lib/elixir_poolboy_example.ex

@@ -39,7 +39,8 @@ defmodule ElixirPoolboyExample do
   defp pool_square(x) do
     :poolboy.transaction(
       pool_name(),
-      fn(pid) -> :gen_server.call(pid, x) end
+      fn(pid) -> :gen_server.call(pid, x) end,
+      :infinity
     )
   end
 end

lib/elixir_poolboy_example/worker.ex

@@ -10,6 +10,7 @@ defmodule ElixirPoolboyExample.Worker do
   end
 
   def handle_call(data, from, state) do
+    :timer.sleep(2000)
     result = ElixirPoolboyExample.Squarer.square(data)
     IO.puts "Worker Reports: #{data} * #{data} = #{result}"
     {:reply, [result], state}