Add a comment regarding the `NoTLS` setting.

go-sendxmpp.go

@@ -331,10 +331,16 @@ func main() {
 		DialTimeout: 1 * time.Second,
 		Resource:    resource,
 		Password:    password,
-		NoTLS:       !*flagDirectTLS,
-		StartTLS:    !*flagDirectTLS,
-		Debug:       *flagDebug,
-		TLSConfig:   &tlsConfig,
+		// NoTLS doesn't mean that no TLS is used at all but that instead
+		// of using an encrypted connection to the server (direct TLS)
+		// an unencrypted connection is established. As StartTLS is
+		// set when NoTLS is set go-sendxmpp won't use unencrypted
+		// client-to-server connections.
+		// See https://pkg.go.dev/github.com/mattn/go-xmpp#Options
+		NoTLS:     !*flagDirectTLS,
+		StartTLS:  !*flagDirectTLS,
+		Debug:     *flagDebug,
+		TLSConfig: &tlsConfig,
 	}
 
 	// Read message from file.