use go 1.15

.github/workflows/coverage.yml

@@ -52,6 +52,10 @@ jobs:
         with:
           name: "${{ github.sha }}-${{ matrix.part }}"
         if: env.GIT_DIFF
+      - name: Set up Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: 1.15
       - name: test & coverage report creation
         run: |
           cat pkgs.txt.part.${{ matrix.part }} | xargs go test -mod=readonly -timeout 8m -race -coverprofile=${{ matrix.part }}profile.out -covermode=atomic