Providing full test matrix in GitHub actions

Starting with Go 1.7, since this is the lowest version still working, once we merge in #12. We can then gradually move upwards.

Author: oxisto

.github/workflows/build.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go: [1.14, 1.15, 1.16]
+        go: [1.7, 1.8, 1.9, 1.10, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16]
     steps:
       - name: Checkout
         uses: actions/checkout@v2