CI: Run tests on Go 1.17+

Add in a ^1.17.0 go-version for the actions/setup-go@v2 action. This
was set for our build step but not for the step that runs all of the
unit tests.

Signed-off-by: Daniel Canter <dcanter@microsoft.com>

.github/workflows/ci.yml

@@ -12,6 +12,8 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-go@v2
+        with:
+          go-version: '^1.17.0'
       - run: go test -gcflags=all=-d=checkptr -v ./...
 
   build: