Update docker go build version to 1.21 (#1758)

Dockerfile

@@ -1,7 +1,7 @@
 # Dockerfile References: https://docs.docker.com/engine/reference/builder/
 
 # Start from the latest golang base image
-FROM golang:1.20-alpine as builder
+FROM golang:1.21-alpine as builder
 
 # Set the Current Working Directory inside the container
 WORKDIR /app