feat: logging different levels with slog

main.go

@@ -2,7 +2,7 @@ package main
 
 import (
 	"crypto/subtle"
-	"log"
+	"log/slog"
 	"net/http"
 	"net/http/httputil"
 	"net/url"
@@ -11,6 +11,9 @@ import (
 )
 
 func main() {
+	logger := slog.New(slog.NewJSONHandler(os.Stdout, nil))
+	slog.SetDefault(logger)
+
 	target := mustEnv("PZ8_RELAY_TARGET_URL")
 	username := mustEnv("PZ8_RELAY_USERNAME")
 	password := mustEnv("PZ8_RELAY_PASSWORD")
@@ -22,7 +25,8 @@ func main() {
 
 	targetURL, err := url.Parse(target)
 	if err != nil {
-		log.Fatalf("invalid PZ8_RELAY_TARGET_URL: %v", err)
+		slog.Error("invalid PZ8_RELAY_TARGET_URL", "err", err)
+		os.Exit(1)
 	}
 
 	proxy := &httputil.ReverseProxy{
@@ -35,7 +39,7 @@ func main() {
 		u, p, ok := r.BasicAuth()
 		if !ok || subtle.ConstantTimeCompare([]byte(u), []byte(username)) != 1 ||
 			subtle.ConstantTimeCompare([]byte(p), []byte(password)) != 1 {
-			log.Printf("unauthorized request from %s", clientIP(r))
+			slog.Warn("unauthorized request", "client", clientIP(r))
 			w.Header().Set("WWW-Authenticate", `Basic realm="pz8-relay"`)
 			http.Error(w, "unauthorized", http.StatusUnauthorized)
 			return
@@ -43,8 +47,11 @@ func main() {
 		proxy.ServeHTTP(w, r)
 	})
 
-	log.Printf("pz8-relay listening on %s, proxying to %s", addr, targetURL.Redacted())
+	slog.Info("pz8-relay listening", "addr", addr, "target", targetURL.Redacted())
-	log.Fatal(http.ListenAndServe(addr, nil))
+	if err := http.ListenAndServe(addr, nil); err != nil {
+		slog.Error("server stopped", "err", err)
+		os.Exit(1)
+	}
 }
 
 // clientIP returns the original client address, trusting X-Forwarded-For
@@ -62,7 +69,8 @@ func clientIP(r *http.Request) string {
 func mustEnv(key string) string {
 	v := os.Getenv(key)
 	if v == "" {
-		log.Fatalf("missing required env var: %s", key)
+		slog.Error("missing required env var", "name", key)
+		os.Exit(1)
 	}
 	return v
 }