Replace place holders in Golang Viper

viper_util.go

// after viper read config, replace all placeholders with values

func ReplacePlaceHolders() {
	r, _ := regexp.Compile("\\${[a-zA-Z0-9.: _]+}")
	replacer := func(placeHolder []byte) []byte {
		name := string(placeHolder)
		name = name[2 : len(name)-1]
		index := strings.Index(name, ":")
		if index != -1 {
			defaultValue := name[index+1:]
			name = name[0:index]
			value := viper.GetString(name)
			if value == "" {
				value = defaultValue
			}
			return []byte(value)
		} else {
			return []byte(viper.GetString(name))
		}

	}
	for _, k := range viper.AllKeys() {
		value := viper.GetString(k)
		if strings.Contains(value, "${") && strings.Contains(value, "}") {
			newValue := r.ReplaceAllFunc([]byte(value), replacer)
			viper.Set(k, string(newValue))
		}
	}
}