Update manual build to Go 1.16

Author: cedricziel

.github/workflows/manual-build.yml

@@ -6,6 +6,10 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
+      - name: Set up Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: 1.16
       - name: Run GoReleaser
         uses: goreleaser/goreleaser-action@v2
         with: