If you have kubeconfig file already in place,

kubeconfig := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(clientcmd.NewDefaultClientConfigLoadingRules(), &clientcmd.ConfigOverrides{})

There is one more function clientcmd.NewInteractiveDeferredLoadingClientConfig but as per code, we can use it only when password is allowed

namespace, _, err := kubeconfig.Namespace()
restconfig, err := kubeconfig.ClientConfig()
clientcmdapi.Config, err := kubeconfig.RawConfig()

Here, kubeconfig is interface of following type:

// ClientConfig is used to make it easy to get an api server client
type ClientConfig interface {
	// RawConfig returns the merged result of all overrides
	RawConfig() (clientcmdapi.Config, error)
	// ClientConfig returns a complete client config
	ClientConfig() (*restclient.Config, error)
	// Namespace returns the namespace resulting from the merged
	// result of all overrides and a boolean indicating if it was
	// overridden
	Namespace() (string, bool, error)
	// ConfigAccess returns the rules for loading/persisting the config.
	ConfigAccess() ConfigAccess

structs NewNonInteractiveDeferredLoadingClientConfig & inClusterClientConfig implements above interface and can be used as per requirements whether inside of cluster or outside.