Clean cache during CI tests (#307)

Author: teivah

.github/workflows/ci.yml

@@ -19,4 +19,4 @@ jobs:
         with:
           version: v1.29
       - name: Test
-        run: go test -race -timeout 10s ./...
+        run: go clean -testcache ./... && go test -race -timeout 10s ./...