Golang Viper：如果第一个字段不存在，如何从另一个字段获取值

I need to read data first of all from the fields inside the service, and only then look at the external fields.个

存在此类型的配置:

auth_service:
  log_level: debug
  port: 9999
mail_service:
  log_level: debug
  port: 9998
smtp:
  host: localhost
  port: 1025
  username: ""
  password: ""
  email_from: "mailservice@test.test"
  retries_count: 5
log_level: test

我试图通过viper.RegisterAlias("log_level", "auth_service.log_level")来实现，但在这种形式下，外部字段是不能读取的.

获取配置的代码如下:

type Config struct  {
    LogLevel string `mapstructure:"log_level"`
    Port int `mapstructure:"port"`
    SMTP SMTPConfig `mapstructure:"smtp"`
}

type SMTPConfig struct {
    Host         string     `mapstructure:"host"`
    Port         int        `mapstructure:"port"`
    Username     string     `mapstructure:"username"`
    Password     string     `mapstructure:"password"`
    EmailFrom    string     `mapstructure:"email_from"`
    RetriesCount int        `mapstructure:"retries_count"`
}

func LoadConfig(path string) (*Config, error) {
    type ServiceConfig struct {
        Cfg Config `mapstructure:"auth_service"`
    }
    viper.RegisterAlias("log_level","auth_service.log_level")
    viper.AutomaticEnv()
    if path != "" {
        dir := p.Dir(path)
        file := p.Base(path)
        fileParts := strings.Split(file, ".")
        if len(fileParts) != 2 {
            return nil, fmt.Errorf("incorrect config file: %s", file)
        }
        viper.AddConfigPath(dir)
        viper.SetConfigName(fileParts[0])
        viper.SetConfigType(fileParts[1])
        err := viper.ReadInConfig()
        if err != nil {
            return nil, err
        }
    }
    fmt.Println(viper.AllKeys())
    var config ServiceConfig
    err := viper.Unmarshal(&config)
    if err != nil {
        return nil, err
    }
    return &config.Cfg, nil
}

需要ServiceConfig，这样您才能从SERVICE_NAME_FIELD_NAME获得值，因为mapstructure:"service_name.field"不起作用.