executable file not found in $PATH

[hopewise]

I am getting this error when trying to view it in the browser:

RequestId: 3f848f5e-4cb4-4820-aa55-fef28313dfd5 Error: exec: "Elixir.NgspiceProxy:hello_world": executable file not found in $PATH
Runtime.InvalidEntrypoint

At Lambda setup:

ENTRYPOINT override Elixir.NgspiceProxy:hello_world

here is my entrypoint: lib/ngspice_proxy.ex

defmodule NgspiceProxy do
  @moduledoc """
  Entrypoint for my hello world Lambda function.
  """

  require Logger

  @doc """
  The lambda entrypoint is just a public function in a module which accepts
  two maps.
  The returned term will be passed to Poison for Json Encoding.
  """
  @spec hello_world(Map.t(), Map.t()) :: Term
  def hello_world(request, context) when is_map(request) and is_map(context) do
    """
    Hello World!
    Got reqeust #{Kernel.inspect(request)}
    Got Context #{Kernel.inspect(context)}
    """
    |> Logger.info()

    :ok
  end
end

mix.exs

defmodule NgspiceProxy.MixProject do
  use Mix.Project

  def project do
    [
      app: :ngspice_proxy,
      version: "0.1.0",
      elixir: "~> 1.5",
      elixirc_paths: elixirc_paths(Mix.env()),
      compilers: [:phoenix, :gettext] ++ Mix.compilers(),
      start_permanent: Mix.env() == :prod,
      aliases: aliases(),
      deps: deps()
    ]
  end

  def application do
    [
      mod: {NgspiceProxy.Application, []},
      extra_applications: [:logger, :runtime_tools, :edeliver],

    ]
  end

  defp deps do
    [
      {:aws_lambda_elixir_runtime, "~> 0.1.0"},
      {:phoenix, "~> 1.4.7"},
      {:phoenix_pubsub, "~> 1.1"},
      {:phoenix_html, "~> 2.11"},
      {:phoenix_live_reload, "~> 1.2", only: :dev},
      {:gettext, "~> 0.11"},
      {:jason, "~> 1.0"},
      {:plug_cowboy, "~> 2.0"},
      {:temp, "~> 0.4"},
      {:cortex, "~> 0.1", only: [:dev, :test]},
      {:edeliver, ">= 1.6.0"},
      {:distillery, "~> 2.1.1"},
      {:mix_deploy, "~> 0.1.0"},
      {:rename, "~> 0.1.0", only: :dev}
    ]
  end

  defp aliases do
    [
      "ecto.setup": ["ecto.create", "ecto.migrate", "run priv/repo/seeds.exs"],
      "ecto.reset": ["ecto.drop", "ecto.setup"],
      test: ["ecto.create --quiet", "ecto.migrate", "test"]
    ]
  end
end

Dockerfile

FROM elixir:1.6.6-otp-21 as build
RUN apt-get update
RUN apt-get install -y inotify-tools

WORKDIR /app
COPY . /app
RUN mix local.hex --force
RUN mix local.rebar --force
RUN mix deps.get

RUN mix compile.phoenix

FROM elixir:1.6.6-otp-21-alpine as final
RUN apk update && apk add inotify-tools

WORKDIR /app
COPY --from=build /app .
COPY --from=build /usr/bin/ngspice /usr/bin/ngspice

ENV PATH="${PATH}:/app"

EXPOSE 8080

CMD ["mix", "phx.server"]

Any idea ?