Check the DB during /status/alive calls

lib/nerves_hub_web/plugs/im_alive.ex

@@ -9,11 +9,18 @@ defmodule NervesHubWeb.Plugs.ImAlive do
   def init(config), do: config
 
   def call(%{request_path: "/status/alive"} = conn, _) do
+    case Ecto.Adapters.SQL.query(NervesHub.Repo, "SELECT true", []) do
+      {:ok, _} -> send_result(conn, 200, "Hello, Friend!")
+      _result -> send_result(conn, 500, "Sorry, Friend :(")
+    end
+  end
+
+  def call(conn, _), do: conn
+
+  defp send_result(conn, code, message) do
     conn
     |> put_resp_content_type("text/plain")
-    |> send_resp(200, "Hello Friend!")
+    |> send_resp(code, message)
     |> halt
   end
-
-  def call(conn, _), do: conn
 end