fix: adjust some code structure to satisfy linter

main.go

@@ -1,7 +1,7 @@
 package main
 
 import (
-	"log"
+	"log/slog"
 	"net/http"
 	"os"
 	"os/signal"
@@ -24,7 +24,7 @@ func main() {
 	cli := cmd.CLI{}
 	config, err := cli.Parse()
 	if err != nil {
-		log.Fatal(err)
+		panic(err)
 	}
 
 	handleGracefulShutdown()
@@ -38,15 +38,16 @@ func main() {
 	ctx := downloader.NewContext(config.DataFile, config.DataURL)
 	if !ctx.FileExists() {
 		if downloadErr := ctx.Download(); downloadErr != nil {
-			log.Fatal(downloadErr)
+			panic(err)
 		}
-		log.Printf("saved file to %s\n", ctx.Filename)
+		slog.Info("saved file", "path", ctx.Filename)
 	}
 
 	cache := cache.NewCache(config.CacheTTL)
 	db, err := database.NewDatabase(config)
 	if err != nil {
-		log.Fatal("database creation failed", err)
+		slog.Error("database creation failed")
+		panic(err)
 	}
 
 	if config.EnableExporter {
@@ -66,23 +67,24 @@ func main() {
 				}
 			}
 		}()
-		log.Println("prometheus exporter refreshes metric data every", config.ExporterInterval)
+		slog.Info("prometheus exporter refreshes metric data", "interval", config.ExporterInterval)
 
 		go func() {
 			err = exporter.Start()
 			if err != nil {
-				log.Panic(err)
+				panic(err)
 			}
 		}()
-		log.Println("prometheus exporter started at", config.ExporterAddress)
+		slog.Info("prometheus exporter started", "address", config.ExporterAddress)
 	}
 
-	log.Println("importing data from file", config.DataFile)
+	slog.Info("importing data from file", "path", config.DataFile)
 	err = csvimporter.ImportCSV(config.DataFile, db)
 	if err != nil {
-		log.Fatal("data Import from file failed", err)
+		slog.Error("data import from file failed")
+		panic(err)
 	}
-	log.Println("imported data from file successful")
+	slog.Info("imported data from file successfully")
 
 	lh := apiv1.NewLocationHandler(cache, db)
 	r.Mount("/api/v1", apiv1.NewRouter(lh))
@@ -93,9 +95,9 @@ func main() {
 		ReadHeaderTimeout: config.ReadHeaderTimeout,
 	}
 
-	log.Println("starting server at", server.Addr)
+	slog.Info("starting server", "address", server.Addr)
 	if err = server.ListenAndServe(); err != nil {
-		log.Panic(err)
+		panic(err)
 	}
 }
 
@@ -106,7 +108,7 @@ func handleGracefulShutdown() {
 
 	go func() {
 		sig := <-signals
-		log.Printf("caught signal: %+v", sig)
+		slog.Info("caught signal", "signal", sig)
 		os.Exit(0)
 	}()
 }