Add -config flag using cobra to specify config file path

cmd/pixad/main.go

@@ -2,6 +2,10 @@
 package main
 
 import (
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
 	"go.uber.org/fx"
 	"sneak.berlin/go/pixa/internal/config"
 	"sneak.berlin/go/pixa/internal/database"
@@ -19,11 +23,33 @@ var (
 	Buildarch string    //nolint:gochecknoglobals // set by ldflags
 )
 
+var configPath string //nolint:gochecknoglobals // cobra flag
+
 func main() {
+	rootCmd := &cobra.Command{
+		Use:   "pixad",
+		Short: "Pixa image caching proxy server",
+		Run:   run,
+	}
+
+	rootCmd.Flags().StringVarP(&configPath, "config", "c", "", "path to config file")
+
+	if err := rootCmd.Execute(); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
+
+func run(_ *cobra.Command, _ []string) {
 	globals.Appname = Appname
 	globals.Version = Version
 	globals.Buildarch = Buildarch
 
+	// Set config path in environment if specified via flag
+	if configPath != "" {
+		_ = os.Setenv("PIXA_CONFIG_PATH", configPath)
+	}
+
 	fx.New(
 		fx.Provide(
 			config.New,