[#44] node: Support multiple configs

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

pkg/util/config/dir.go

@@ -0,0 +1,55 @@
+package config
+
+import (
+	"os"
+	"path"
+
+	"github.com/spf13/viper"
+)
+
+// ReadConfigDir reads all config files from provided directory in alphabetical order
+// and merge its content with current viper configuration.
+func ReadConfigDir(v *viper.Viper, configDir string) error {
+	entries, err := os.ReadDir(configDir)
+	if err != nil {
+		return err
+	}
+
+	for _, entry := range entries {
+		if entry.IsDir() {
+			continue
+		}
+		ext := path.Ext(entry.Name())
+		if ext != ".yaml" && ext != ".yml" {
+			continue
+		}
+
+		if err = mergeConfig(v, path.Join(configDir, entry.Name())); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// mergeConfig reads config file and merge its content with current viper.
+func mergeConfig(v *viper.Viper, fileName string) (err error) {
+	var cfgFile *os.File
+	cfgFile, err = os.Open(fileName)
+	if err != nil {
+		return err
+	}
+
+	defer func() {
+		errClose := cfgFile.Close()
+		if err == nil {
+			err = errClose
+		}
+	}()
+
+	if err = v.MergeConfig(cfgFile); err != nil {
+		return err
+	}
+
+	return nil
+}