ci.yml in enum_ish-1.6.1

- old
+ new
@@ -2,29 +2,43 @@
 
 on: [push, pull_request]
 
 jobs:
   test:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     strategy:
       fail-fast: false
       matrix:
-        ruby: [2.3, 2.4, 2.5, 2.6, 2.7, 3.0]
-        gemfile: ['rails50', 'rails51', 'rails52', 'rails60', 'rails61']
+        ruby: [2.3, 2.4, 2.5, 2.6, 2.7, '3.0', 3.1]
+        gemfile: ['rails50', 'rails51', 'rails52', 'rails60', 'rails61', 'rails70']
         exclude:
           - ruby: 2.3
             gemfile: rails60
           - ruby: 2.3
             gemfile: rails61
+          - ruby: 2.3
+            gemfile: rails70
           - ruby: 2.4
             gemfile: rails60
           - ruby: 2.4
             gemfile: rails61
+          - ruby: 2.4
+            gemfile: rails70
+          - ruby: 2.5
+            gemfile: rails70
+          - ruby: 2.6
+            gemfile: rails70
           - ruby: 3.0
             gemfile: rails50
           - ruby: 3.0
             gemfile: rails51
           - ruby: 3.0
+            gemfile: rails52
+          - ruby: 3.1
+            gemfile: rails50
+          - ruby: 3.1
+            gemfile: rails51
+          - ruby: 3.1
             gemfile: rails52
 
     name: ruby ${{ matrix.ruby }}, ${{ matrix.gemfile }}
 
     env: