feat: fix CI, replace deprecated go get with go install for goveralls (#35)

Author: hsluoyz

.github/workflows/ci.yml

@@ -39,9 +39,7 @@ jobs:
         run: go test -covermode atomic -coverprofile=covprofile ./...
 
       - 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: