Add ubuntu latest and ubuntu 20.04 to integration test (#30)

* Add ubuntu latest and ubuntu 20.04 to integration test

* Update bats to bats-core

.github/workflows/go.yml

@@ -11,7 +11,7 @@ jobs:
   build:
     strategy:
       matrix:
-        os: [ubuntu-18.04]
+        os: [ubuntu-latest, ubuntu-20.04, ubuntu-18.04]
     
     runs-on: ${{ matrix.os }}
 
@@ -47,9 +47,8 @@ jobs:
 
     - name: Install Bats
       run: |
-        sudo add-apt-repository ppa:duggan/bats --yes
-        sudo apt-get update -qq
-        sudo apt-get install -qq bats
+        sudo apt install npm
+        sudo npm install -g bats
 
     - name: Install Docker
       run: |