[actions] revert build/test/lint step to 1.15.6

.github/workflows/release.yml

@@ -20,7 +20,7 @@ jobs:
         name: Setup Go
         uses: actions/setup-go@v2
         with:
-          go-version: '^1.16.0'
+          go-version: '^1.15.6'
       -
         name: Install Deps
         id: install-deps

.github/workflows/test.yml

@@ -18,7 +18,7 @@ jobs:
       - name: Setup Go
         uses: actions/setup-go@v2
         with:
-          go-version: '^1.16.0'
+          go-version: '^1.15.6'
       - name: Install Deps
         id: install-deps
         run: sudo apt-get -y install libpcsclite-dev