test with Java 20

Author: forax

.github/workflows/main.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on:  ubuntu-latest
     strategy:
       matrix:
-        java: [ '17', 'ea' ]
+        java: [ '17', '20' ]
     name: Java ${{ matrix.Java }} sample
     steps:
       - uses: actions/checkout@v3