FromEnv reads config from environment variables, and unmarshal to config prefix is the prefix of environment variables: type MyConfig struct { Foo struct { Bar string } } config := MyConfig{} config.Init(&config, FromEnv("MYAPP")) will read `config.Foo.Bar` from env `MYAPP_FOO_BAR`.

FromFile reads config from file at path, and unmarshal to config.

Init reads configure, write values into given configModel - FromFile: read config from file - FromEnv: read config from environment variables - WatchFileChange: watch config file and reload config when changed.

WatchFileChange works with FromFile: var config MyConfig config.Init(&config, FromFile(path), WatchFileChange(hook)) WatchFileChange watch current viper config file, and reload config when changed.

BaseConfig includes common config for services.

DBConfig is the configurations for connecting database.

HTTPConfig is the configurations for HTTP server.