added domain support and more verbose logging and better tls determination

main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"context"
+	"crypto/tls"
 	"flag"
 	"log"
 	"net"
@@ -15,6 +16,7 @@ type Config struct {
 	StaticIP         string
 	Port             string
 	UseHTTPS         bool
+	Domain           string
 	NormalInterval   time.Duration
 	FailInterval     time.Duration
 	Timeout          time.Duration
@@ -105,6 +107,7 @@ func parseFlags() *Config {
 	flag.StringVar(&cfg.StaticIP, "ip", "", "Static IP to check")
 	flag.StringVar(&cfg.Port, "port", "80", "Port to check")
 	flag.BoolVar(&cfg.UseHTTPS, "https", false, "Use HTTPS")
+	flag.StringVar(&cfg.Domain, "domain", "", "Domain for HTTPS SNI/Host")
 	flag.DurationVar(&cfg.NormalInterval, "interval", 120*time.Second, "Normal check interval")
 	flag.DurationVar(&cfg.FailInterval, "fail-interval", 10*time.Second, "Interval during failure detection")
 	flag.DurationVar(&cfg.Timeout, "timeout", 5*time.Second, "HTTP timeout")
@@ -139,18 +142,37 @@ func checkHealth(cfg *Config) bool {
 		},
 	}
 
+	if cfg.UseHTTPS && cfg.Domain != "" {
+		transport.TLSClientConfig = &tls.Config{
+			ServerName: cfg.Domain,
+		}
+	}
+
 	client := &http.Client{
 		Transport: transport,
 		Timeout:   cfg.Timeout,
 	}
 
-	req, _ := http.NewRequestWithContext(ctx, "GET", scheme+"://"+cfg.StaticIP+cfg.HealthURL, nil)
+	host := cfg.StaticIP
+	if cfg.UseHTTPS && cfg.Domain != "" {
+		host = cfg.Domain
+	}
+
+	req, _ := http.NewRequestWithContext(ctx, "GET", scheme+"://"+host+cfg.HealthURL, nil)
+
+	if cfg.UseHTTPS && cfg.Domain != "" {
+		req.Host = cfg.Domain
+	}
 
 	resp, err := client.Do(req)
 	if err != nil {
 		return false
 	}
-	defer resp.Body.Close()
+	defer func() {
+		if err := resp.Body.Close(); err != nil && cfg.Verbose {
+			log.Println("body close:", err)
+		}
+	}()
 
 	return resp.StatusCode == 200
 }