modification macos -> linux

.circleci/config.yml

@@ -1,8 +1,11 @@
 version: 2.1
 jobs:
   build:
+    docker:
+      - image: cimg/node:14.10.1 # the primary container, where your job's commands are run
+        auth:
+          username: mydockerhub-user
+          password: $DOCKERHUB_PASSWORD  # context / project UI env-var reference
     steps:
       - checkout # check out the code in the project directory
       - run: echo "hello world" # run the `echo` command
-    macos:
-      xcode: 10.1.0