Add python3.7 test back, based on review comment

Signed-off-by: Yong Tang <[email protected]>

Author: yongtang

.github/workflows/build.yml

@@ -179,7 +179,7 @@ jobs:
     runs-on: macos-latest
     strategy:
       matrix:
-        python: ['3.8']
+        python: ['3.7', '3.8']
     steps:
       - uses: actions/checkout@v2
       - uses: docker-practice/actions-setup-docker@v1
@@ -275,8 +275,13 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-20.04]
-        python: ['3.8']
+        os: [ubuntu-18.04, ubuntu-20.04]
+        python: ['3.7', '3.8']
+        exclude:
+          - os: ubuntu-18.04
+            python: '3.8'
+          - os: ubuntu-20.04
+            python: '3.7'
     steps:
       - uses: actions/checkout@v2
       - uses: actions/download-artifact@v1
@@ -370,7 +375,7 @@ jobs:
     runs-on: windows-latest
     strategy:
       matrix:
-        python: ['3.8']
+        python: ['3.7', '3.8']
     steps:
       - uses: actions/checkout@v2
       - uses: actions/download-artifact@v1