macOS: add config file search path

this way the default config file is used in brew package if no config file is
set

Signed-off-by: Nicola Murino <nicola.murino@gmail.com>

config/config_darwin.go

@@ -0,0 +1,25 @@
+// Copyright (C) 2019-2022  Nicola Murino
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published
+// by the Free Software Foundation, version 3.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+//go:build darwin
+// +build darwin
+
+package config
+
+import "github.com/spf13/viper"
+
+// macOS specific config search path
+func setViperAdditionalConfigPaths() {
+	viper.AddConfigPath("/usr/local/etc/sftpgo")
+}