action: update go builder version to 1.16

Author: lbscorpio

.github/workflows/iso-ci.yaml

@@ -14,7 +14,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        go: ["1.15"]
+        go: ["1.16"]
     steps:
     - uses: actions/setup-go@v2
       with: