func ServerAPIVersions(c *Config) (groupVersions []string, err error) {
	transport, err := TransportFor(c)
	if err != nil {
		return nil, err
	}
	client := http.Client{Transport: transport}
	configCopy := *c
	configCopy.GroupVersion = nil
	configCopy.APIPath = ""
	baseURL, _, err := defaultServerUrlFor(&configCopy)
	if err != nil {
		return nil, err
	}
	originalPath := baseURL.Path
	baseURL.Path = path.Join(originalPath, legacyAPIPath)
	resp, err := client.Get(baseURL.String())
	if err != nil {
		return nil, err
	}
	var v unversioned.APIVersions
	defer resp.Body.Close()
	err = json.NewDecoder(resp.Body).Decode(&v)
	if err != nil {
		return nil, fmt.Errorf("unexpected error: %v", err)
	}
	groupVersions = append(groupVersions, v.Versions...)
	baseURL.Path = path.Join(originalPath, defaultAPIPath)
	resp2, err := client.Get(baseURL.String())
	if err != nil {
		return nil, err
	}
	var apiGroupList unversioned.APIGroupList
	defer resp2.Body.Close()
	err = json.NewDecoder(resp2.Body).Decode(&apiGroupList)
	if err != nil {
		return nil, fmt.Errorf("unexpected error: %v", err)
	}
	for _, g := range apiGroupList.Groups {
		for _, gv := range g.Versions {
			groupVersions = append(groupVersions, gv.GroupVersion)
		}
	}
	return groupVersions, nil
}
TODO: Is this obsoleted by the discovery client?
ServerAPIVersions returns the GroupVersions supported by the API server.
It creates a RESTClient based on the passed in config, but it doesn't rely
on the Version and Codec of the config, because it uses AbsPath and
takes the raw response.
package rest
import (
	"encoding/json"
	"fmt"
	"net/http"
	"path"
	"k8s.io/client-go/pkg/api/unversioned"
)
const (
	legacyAPIPath  = "/api"
	defaultAPIPath = "/apis"
)