remove mutex collection; added redis-based mutex

Author: mmasiukevich

.travis.yml

@@ -4,6 +4,9 @@ php:
   - 7.3
   - 7.4snapshot
 
+services:
+  - redis-server
+
 cache:
   directories:
     - $HOME/.cache/composer

composer.json

@@ -29,7 +29,8 @@
   "require": {
     "php": ">=7.3",
     "amphp/amp": "v2.4.*",
-    "amphp/file": "v1.0.*"
+    "amphp/file": "v1.0.*",
+    "amphp/redis": "v1.0.*"
   },
   "require-dev": {
     "php-service-bus/code-style-config": "v1.2.*",