dep: upgrade to go1.21

Author: yeqown

.github/workflows/go.yml

@@ -16,7 +16,7 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@v2
       with:
-        go-version: 1.18
+        go-version: 1.21
 
     - name: Test
       run: go test $(go list ./... | grep -v examples)