chore: update go to 1.21.6

Author: hedhyw

.github/workflows/check.yml

@@ -14,7 +14,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.21.3'
+          go-version: '1.21.6'
         id: go
 
       - name: Check out code into the Go module directory

.github/workflows/release.yml

@@ -15,7 +15,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.21.3'
+          go-version: '1.21.6'
 
       - name: Fetch vendor
         run: make vendor