chore(deps): update alpine docker tag to v3.21.0 (#27)

hello-world-app/Dockerfile

@@ -2,7 +2,7 @@ FROM golang:latest AS builder
 COPY ./hello-world.go .
 RUN  go env -w CGO_ENABLED=0 GO111MODULE=off && go build -o /app/hello-world
 
-FROM alpine:3.20.3
+FROM alpine:3.21.0
 WORKDIR /app
 COPY --from=builder /app/hello-world .
 EXPOSE 8080