single-file-webserver.exs

Mix.install([{:bandit, "~> 1.0"}])

defmodule WebServer do
  import Plug.Conn

  def init(opts), do: opts

  def call(conn, _opts) do
    case conn.path_info do
      [] ->
        conn
        |> send_resp(200, "Hello World")
        |> halt()

      path ->
        conn
      |> send_resp(200, "Hello #{Enum.join(path, ", ")}")
      |> halt()
    end
  end
end

Bandit.start_link(plug: WebServer)

Process.sleep(:infinity)