build docker image from scratch to reduce runtime dependencies

Dockerfile

@@ -1,14 +1,17 @@
 
-FROM registry.access.redhat.com/ubi8/ubi-minimal AS builder
-RUN microdnf install -y shadow-utils && microdnf clean all
-RUN set -o pipefail && groupadd -r -g 1000 gouser && useradd -r -u 1000 -g gouser -m -d /opt/gouser -s /bin/bash gouser && cat /etc/passwd | grep gouser > /etc/passwd_gouser
+FROM alpine AS builder
+RUN apk update && apk upgrade && apk add --no-cache ca-certificates
+RUN update-ca-certificates
+RUN set -o pipefail && addgroup --gid 1000 gouser && adduser --disabled-password --no-create-home --ingroup gouser gouser
+RUN cat /etc/passwd
+RUN cat /etc/passwd | grep gouser > /etc/passwd_gouser
 
 FROM scratch
 ARG VERSION
 ENV VERSION=${VERSION}
 COPY noah-mqtt /
 COPY LICENSE /
-COPY --from=builder /etc/pki/tls/certs/ca-bundle.crt /etc/pki/tls/certs/
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
 COPY --from=builder /etc/passwd_gouser /etc/passwd
 USER gouser
 ENTRYPOINT ["/noah-mqtt"]

cmd/noah-mqtt/main.go

@@ -6,12 +6,18 @@ import (
 	"noah-mqtt/internal/service"
 	"os"
 	"os/signal"
+	"os/user"
 	"syscall"
 )
 
 func main() {
 	cfg := config.Get()
 	slog.Info("noah-mqtt started", slog.String("version", cfg.Version))
+
+	if currentUser, err := user.Current(); err == nil {
+		slog.Info("running as", slog.String("username", currentUser.Username), slog.String("uid", currentUser.Uid))
+	}
+
 	service.Start()
 
 	cancelChan := make(chan os.Signal, 1)