Drop dependency on mutex_m

Author: byroot

lib/github_authentication/provider.rb

@@ -1,28 +1,25 @@
 # frozen_string_literal: true
-require "mutex_m.rb"
-
 require 'github_authentication/retriable'
 
 module GithubAuthentication
   class Provider
     include Retriable
-    include Mutex_m
 
     Error = Class.new(StandardError)
     TokenGeneratorError = Class.new(Error)
 
     def initialize(generator:, cache:)
-      super()
       @token = nil
       @generator = generator
       @cache = cache
+      @mutex = Mutex.new
     end
 
     def token(seconds_ttl: 5 * 60)
       return @token if @token&.valid_for?(seconds_ttl)
 
       with_retries(TokenGeneratorError) do
-        mu_synchronize do
+        @mutex.synchronize do
           return @token if @token&.valid_for?(seconds_ttl)
 
           if (@token = @cache.read)