Add tzdata in container

Dockerfile

@@ -12,6 +12,8 @@ RUN go get -d -v && \
 
 FROM alpine
 
+RUN apk add --no-cache tzdata
+
 CMD ["linky2influx"]
 
 COPY --from=gobuild /go/src/git.nemunai.re/linky2influx/linky2influx /usr/bin/linky2influx

config.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"strings"
+)
+
+func parseEnvironmentVariables() (err error) {
+	for _, line := range os.Environ() {
+		if strings.HasPrefix(line, "LINKY2INFLUX_") {
+			err := parseConfigLine(line)
+			if err != nil {
+				return fmt.Errorf("error in environment (%q): %w", line, err)
+			}
+		}
+	}
+	return
+}
+
+func parseConfigLine(line string) (err error) {
+	fields := strings.SplitN(line, "=", 2)
+	orig_key := strings.TrimSpace(fields[0])
+	value := strings.TrimSpace(fields[1])
+
+	if len(value) == 0 {
+		return
+	}
+
+	key := strings.TrimPrefix(orig_key, "LINKY2INFLUX_")
+	key = strings.Replace(key, "_", "-", -1)
+	key = strings.ToLower(key)
+
+	err = flag.Set(key, value)
+
+	return
+}

main.go

@@ -184,6 +184,8 @@ func main() {
 	var pushFrequency = flag.Bool("push-frequency", false, "Also fetch data about the grid frequency")
 	flag.Parse()
 
+	parseEnvironmentVariables()
+
 	if len(flag.Args()) < 1 {
 		log.Println("missing required argument: serial device (eg. /dev/ttyUSB0)")
 		return