update help and docs

Author: Snawoot

README.md

@@ -18,6 +18,7 @@ Dumbest HTTP proxy ever.
 * Supports HTTP/2
 * Resilient to DPI (including active probing, see `hidden_domain` option for authentication providers)
 * Connecting via upstream HTTP(S)/SOCKS5 proxies (proxy chaining)
+* systemd socket activation
 
 ## Installation
 
@@ -184,7 +185,7 @@ Usage of /home/user/go/bin/dumbproxy:
   -autocert-whitelist value
     	restrict autocert domains to this comma-separated list
   -bind-address string
-    	HTTP proxy listen address (default ":8080")
+    	HTTP proxy listen address. Set empty value to use systemd socket activation. (default ":8080")
   -cafile string
     	CA file to authenticate clients with certificates
   -cert string

main.go

@@ -76,7 +76,7 @@ type CLIArgs struct {
 
 func parse_args() CLIArgs {
 	var args CLIArgs
-	flag.StringVar(&args.bind_address, "bind-address", ":8080", "HTTP proxy listen address")
+	flag.StringVar(&args.bind_address, "bind-address", ":8080", "HTTP proxy listen address. Set empty value to use systemd socket activation.")
 	flag.StringVar(&args.auth, "auth", "none://", "auth parameters")
 	flag.IntVar(&args.verbosity, "verbosity", 20, "logging verbosity "+
 		"(10 - debug, 20 - info, 30 - warning, 40 - error, 50 - critical)")