Merge pull request #125 from tetsuharuohzeki/bump-ci

Use Go v16 for CI

.github/workflows/ci.yml

@@ -30,7 +30,7 @@ jobs:
       - name: Set up Go 1.x
         uses: actions/setup-go@v2
         with:
-            go-version: ^1.15 # The Go version to download (if necessary) and use.
+            go-version: ^1.16 # The Go version to download (if necessary) and use.
       - name: build
         run: make build -j
       - name: test