Golang Go语言中结构体套结构体指针--有什么黑魔法么

在看 k8s 源代码时候，有这么一段代码，其中 Complete()方法， 看注释是可以填充没有设置的字段，填充字段需要这么套娃么.

CompletedConfig --》 指针 completedConfig --》 Config 指针

// Config is the main context object for the controller manager.
type Config struct {
	ComponentConfig kubectrlmgrconfig.KubeControllerManagerConfiguration
SecureServing *apiserver.SecureServingInfo
// LoopbackClientConfig is a config for a privileged loopback connection
LoopbackClientConfig *restclient.Config

// TODO: remove deprecated insecure serving
InsecureServing *apiserver.DeprecatedInsecureServingInfo
Authentication  apiserver.AuthenticationInfo
Authorization   apiserver.AuthorizationInfo

// the general kube client
Client *clientset.Clientset

// the client only used for leader election
LeaderElectionClient *clientset.Clientset

// the rest config for the master
Kubeconfig *restclient.Config

// the event sink
EventRecorder record.EventRecorder
}
type completedConfig struct {
*Config
}
// CompletedConfig same as Config, just to swap private object.
type CompletedConfig struct {
// Embed a private pointer that cannot be instantiated outside of this package.
*completedConfig
}
// Complete fills in any fields not set that are required to have valid data. It’s mutating the receiver.
func (c *Config) Complete() *CompletedConfig {
cc := completedConfig{c}
apiserver.AuthorizeClientBearerToken(c.LoopbackClientConfig, &c.Authentication, &c.Authorization)

return &CompletedConfig{&cc}
}