feat: fix CI: use go install for goveralls instead of go get

Author: hsluoyz

.github/workflows/ci.yml

@@ -18,9 +18,7 @@ jobs:
       - name: Run tests
         run: go test -v -coverprofile=./profile.cov ./...
       - name: Install goveralls
-        env:
-          GO111MODULE: off
-        run: go get github.com/mattn/goveralls
+        run: go install github.com/mattn/goveralls@latest
 
       - name: Send coverage
         env: