github: bump go version

Author: bhandras

.github/workflows/main.yml

@@ -20,7 +20,7 @@ env:
 
   # If you change this value, please change it in the following files as well:
   # /Dockerfile
-  GO_VERSION: 1.20.4
+  GO_VERSION: 1.21.4
 
 jobs:
   ########################