Try use JDK 11 as default

Author: liufengyun

.github/workflows/ci.yaml

@@ -15,6 +15,9 @@ jobs:
     container: lampepfl/dotty:2020-04-24
 
     steps:
+      - name: Set up JDK version
+        run: echo "::add-path::/usr/lib/jvm/java-11-openjdk-amd64/bin"
+
       - name: Checkout cleanup script
         uses: actions/checkout@v2
 
@@ -55,6 +58,9 @@ jobs:
     container: lampepfl/dotty:2020-04-24
 
     steps:
+      - name: Set up JDK version
+        run: echo "::add-path::/usr/lib/jvm/java-11-openjdk-amd64/bin"
+
       - name: Checkout cleanup script
         uses: actions/checkout@v2
 
@@ -95,6 +101,9 @@ jobs:
     container: lampepfl/dotty:2020-04-24
 
     steps:
+      - name: Set up JDK version
+        run: echo "::add-path::/usr/lib/jvm/java-11-openjdk-amd64/bin"
+
       - name: Checkout cleanup script
         uses: actions/checkout@v2
 
@@ -174,7 +183,7 @@ jobs:
       - name: Test
         run: ./project/scripts/sbt sbt-dotty/scripted
 
-  test_java11:
+  test_java8:
     runs-on: self-hosted
     container: lampepfl/dotty:2020-04-24
     if: (
@@ -216,13 +225,13 @@ jobs:
 
       - name: Test
         run: |
-          export PATH="/usr/lib/jvm/java-11-openjdk-amd64/bin:$PATH"
+          export PATH="/usr/lib/jvm/java-1.8.0-openjdk-amd64/bin:$PATH"
           ./project/scripts/sbt ";compile ;test"
 
   publish_nightly:
     runs-on: self-hosted
     container: lampepfl/dotty:2020-04-24
-    needs: [test, test_bootstrapped, community_build, test_sbt, test_java11]
+    needs: [test, test_bootstrapped, community_build, test_sbt, test_java8]
     if: github.event_name == 'schedule'
     env:
       NIGHTLYBUILD: yes
@@ -323,7 +332,7 @@ jobs:
   publish_release:
     runs-on: self-hosted
     container: lampepfl/dotty:2020-04-24
-    needs: [test, test_bootstrapped, community_build, test_sbt, test_java11]
+    needs: [test, test_bootstrapped, community_build, test_sbt, test_java8]
     if: github.event_name == 'push' &&
         startsWith(github.event.ref, 'refs/tags/') &&
         !startsWith(github.event.ref, 'refs/tags/sbt-dotty-')
@@ -475,7 +484,7 @@ jobs:
   publish_sbt_release:
     runs-on: self-hosted
     container: lampepfl/dotty:2020-04-24
-    needs: [test, test_bootstrapped, community_build, test_sbt, test_java11]
+    needs: [test, test_bootstrapped, community_build, test_sbt, test_java8]
     if: github.event_name == 'push' &&
         startsWith(github.event.ref, 'refs/tags/sbt-dotty-')