Phoenix, as of version 1.3, included the ability to define fallback controllers or plugs to handle scenarios where a conn is not returned back out. We can harness this to write custom error handling code for our API to catch these scenarios!
We'll start off by creating a new controller called ErrorController for our API. Create lib/vocial_web/controllers/api/error_controller.ex:
defmodule VocialWeb.Api.ErrorController do use VocialWeb, :controllerend
Next, for a handler controller, you need to define a call function that will attempt to look for a conn as the first argument and pattern match against the second argument. We'll just implement a simple 404 handler for purposes of this example:
def call(conn, ...
