Log times in local timezone, run as unprivileged user in Docker image, shrink Docker image

Dockerfile

@@ -1,6 +1,8 @@
 ARG GO_VERSION=1.13
 FROM golang:${GO_VERSION} AS builder
 
+RUN useradd ztdns
+
 WORKDIR /go/src/github.com/mje-nz/ztdns
 
 # Fetch and cache dependencies
@@ -9,18 +11,22 @@ RUN go mod download
 
 # Build static binary
 COPY . .
-RUN CGO_ENABLED=0 GOOS=linux go install
+RUN CGO_ENABLED=0 GOOS=linux go install -ldflags="-w -s"
 
 
-FROM alpine:3.10
+FROM scratch
 
-# We need to add ca-certificates in order to make HTTPS API calls
-RUN apk update && apk add ca-certificates && rm -rf /var/cache/apk/*
+# We need ca-certificates for HTTPS, /etc/passwd to log in, and zoneinfo for
+# time zones
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+COPY --from=builder /etc/passwd /etc/passwd
+COPY --from=builder /usr/share/zoneinfo /usr/share/zoneinfo
 
 WORKDIR /app
-# Copy binary
 COPY --from=builder /go/bin/ztdns .
 
+USER ztdns
+
 ENTRYPOINT ["./ztdns"]
 CMD ["server"]
 EXPOSE 53/udp

cmd/server.go

@@ -75,6 +75,10 @@ var serverCmd = &cobra.Command{
 }
 
 func init() {
+	log.SetFormatter(&log.TextFormatter{
+		TimestampFormat: "2006-01-02 15:04:05 -07:00",
+	})
+
 	RootCmd.AddCommand(serverCmd)
 	serverCmd.Flags().String("interface", "zt0", "network interface to bind to")
 	serverCmd.Flags().Int("port", 53, "port to listen on")