Update versions of go used to run tests

Update the versions of Go used to run tests from 1.13 through 1.17 to
1.15 through 1.19

.github/workflows/go.yml

@@ -6,7 +6,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go: ['1.13', '1.14', '1.15', '1.16', '1.17']
+        go: ['1.15', '1.16', '1.17', '1.18', '1.19']
     steps:
       - uses: actions/checkout@master
       - name: Setup go