Fix depcrecation warnings & CI

.github/workflows/elixir.yml

@@ -10,15 +10,23 @@ jobs:
   build:
     runs-on: ubuntu-latest
 
+    name: Test on OTP ${{matrix.otp}} / Elixir ${{matrix.elixir}}
+    strategy:
+      # Specify the OTP and Elixir versions to use when building
+      # and running the workflow steps.
+      matrix:
+        otp: ['25.2']         # Define the OTP version [required]
+        elixir: ['1.13.4']    # Define the elixir version [required]
+
     steps:
     - uses: actions/checkout@v2
-    - name: Setup elixir
-      uses: actions/setup-elixir@v1
+
+    # Step: Setup Elixir + Erlang image as the base.
+    - name: Set up Elixir
+      uses: erlef/setup-beam@v1
       with:
-        elixir-version: 1.9.4 # Define the elixir version [required]
-        otp-version: 22.2 # Define the OTP version [required]
-    - name: Check formatting
-      run: mix format --check-formatted
+        otp-version: ${{matrix.otp}}
+        elixir-version: ${{matrix.elixir}}
 
     - name: Cache Dependencies
       id: mix-cache

config/config.exs

@@ -1,4 +1,4 @@
-use Mix.Config
+import Config
 
 if Mix.env() == :dev do
   config :mix_test_watch,

test/session_test.exs

@@ -226,7 +226,7 @@ defmodule SessionTest do
       %{
         "event" => "ping"
       },
-      @initial_state()
+      @initial_state
     )
 
     assert_receive {:to_user, %{event: "pong"}}