Update go to 1.21 for CI workflows

Author: tuhaihe

.github/workflows/build_and_unit_test.yml

@@ -17,7 +17,7 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@v4
       with:
-        go-version: 1.19
+        go-version: 1.21
 
     - name: Build
       run: make

.github/workflows/release.yml

@@ -17,7 +17,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v4
         with:
-          go-version: 1.19
+          go-version: 1.21
 
       - name: Build binaries
         run: CGO_ENABLED=0 make