Allow TLSOptions.ServerName use with TLSOptions.SecurityMode (#393)

Author: nsidnev

internal/client/connutils.go

@@ -451,20 +451,19 @@ func (r *configResolver) resolveOptions(
 			"TLSOptions.SecurityMode option")
 	}
 
+	if len(secSources) > 1 {
+		return fmt.Errorf(
+			"mutually exclusive options set in Options: %v",
+			englishList(secSources, "and"))
+	}
+
 	if opts.TLSOptions.ServerName != "" {
-		secSources = append(secSources, "TLSOptions.ServerName")
 		err = r.setTLSServerName(
 			opts.TLSOptions.ServerName,
 			"TLSOptions.ServerName options",
 		)
 	}
 
-	if len(secSources) > 1 {
-		return fmt.Errorf(
-			"mutually exclusive options set in Options: %v",
-			englishList(secSources, "and"))
-	}
-
 	if opts.SecretKey != "" {
 		err = r.setSecretKey(opts.SecretKey, "SecretKey option")
 		if err != nil {