Update workflow to use go1.16

Author: pgavlin

.github/workflows/go.yml

@@ -4,7 +4,7 @@ jobs:
   test:
     strategy:
       matrix:
-        go-version: [1.15.x]
+        go-version: [1.16.x]
         os: [ubuntu-latest, macos-latest, windows-latest]
     env:
       OS: ${{ matrix.os }}