guess and check.

.github/workflows/build.yaml

@@ -20,8 +20,10 @@ jobs:
         uses: actions/checkout@v2
       - name: Test
         run: |
-          mkdir -p $PROJECT_PATH
+          mkdir -p $(dirname "$PROJECT_PATH")
-          cp -a $GITHUB_WORKSPACE/* $PROJECT_PATH/
+          cp -a $GITHUB_WORKSPACE $PROJECT_PATH
+          ls -alt $(dirname "$PROJECT_PATH")
+          ls -alt $PROJECT_PATH
           cd $PROJECT_PATH
 
           go mod vendor