Try to fix TSan

docker/Dockerfile

@@ -1,5 +1,5 @@
 ARG swift_version=5.2
-ARG ubuntu_version=xenial
+ARG ubuntu_version=focal
 ARG base_image=swift:$swift_version-$ubuntu_version
 FROM $base_image
 # needed to do again after FROM due to docker limitation

docker/docker-compose.1804.53.yaml → docker/docker-compose.1604.53.yaml

@@ -3,17 +3,17 @@ version: "3"
 services:
 
   runtime-setup:
-    image: swift-nio-ssh:18.04-5.3
+    image: swift-nio-ssh:16.04-5.3
     build:
       args:
-        ubuntu_version: "bionic"
+        ubuntu_version: "xenial"
         swift_version: "5.3"
 
   test:
-    image: swift-nio-ssh:18.04-5.3
+    image: swift-nio-ssh:16.04-5.3
     environment: []
-      #- SANITIZER_ARG=--sanitize=thread
+      - SANITIZER_ARG=--sanitize=thread
       #- WARN_AS_ERROR_ARG=-Xswiftc -warnings-as-errors
 
   shell:
-    image: swift-nio-ssh:18.04-5.3
+    image: swift-nio-ssh:16.04-5.3

docker/docker-compose.1804.52.yaml

@@ -0,0 +1,19 @@
+version: "3"
+
+services:
+
+  runtime-setup:
+    image: swift-nio-ssh:18.04-5.2
+    build:
+      args:
+        ubuntu_version: "bionic"
+        swift_version: "5.2"
+
+  test:
+    image: swift-nio-ssh:18.04-5.2
+    environment:
+      #- SANITIZER_ARG=--sanitize=thread
+      #- WARN_AS_ERROR_ARG=-warnings-as-errors
+
+  shell:
+    image: swift-nio-ssh:18.04-5.2