Help a Go Newbie

main.go

package main

import (
	"fmt"
	"os"
	"path/filepath"

	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/clientcmd"
)

func loadConfig() (*rest.Config, error) {
	host, port := os.Getenv("KUBERNETES_SERVICE_HOST"), os.Getenv("KUBERNETES_SERVICE_PORT")

	if len(host) == 0 || len(port) == 0 {
		// creates the out-of-cluster config
		fmt.Println("Using out-of-cluster config")
		configFile := filepath.Join(
			os.Getenv("HOME"), ".kube", "config",
		)

		config, err := clientcmd.BuildConfigFromFlags("", configFile)
		if err != nil {
			panic(err.Error())
		}

		return config, nil
	}

	// creates the in-cluster config
	fmt.Println("Using in-cluster config")
	config, err := rest.InClusterConfig()
	if err != nil {
		panic(err.Error())
	}

		return config, nil


	return nil, fmt.Errorf("Could not locate client configuration")
}

func main() {

	config, err := loadConfig()
	// creates the clientset
	clientset, err := kubernetes.NewForConfig(config)
	if err != nil {
		panic(err.Error())
	}

	api := clientset.CoreV1()

	getOptions := metav1.GetOptions{}

	pvc, err := api.PersistentVolumeClaims("webregistry").Get("static-files", getOptions)
	if err != nil {
		panic(err.Error())
	}

	fmt.Print(pvc)

}

output.txt

# The following is the output of the main.go code.
#
# Using the Kubernetes client-go package, the code retrieves a persistent volume claim from the cluster.
#
# I am not sure what data type this is.  It's it a struct?  The "Type" is, unhelpfully "PersistentVolumeClaim", 
# which is why I suspect the struct, I think.
#
# I have found this: https://github.com/kubernetes/client-go/blob/master/kubernetes/typed/core/v1/persistentvolumeclaim.go
# And this: https://godoc.org/k8s.io/client-go/kubernetes/typed/core/v1#CoreV1Client.PersistentVolumeClaims
# And this: https://godoc.org/k8s.io/api/core/v1#PersistentVolumeClaim
# 
# The last link also makes me think what I have is a struct, but it also contains other structs, I think.
#
# I can get at all the values for "item.Name", "item.Status", etc., but have these questions:
#
# 1. What IS this data type - is it in fact a struct?
# 2. How could I iterate or otherwise get the keys themselves, to see what is included in this thing - the "reflect" package?
# 3. What is "ObjectMeta"?  I cannot seem to get or reference it in my code.
# 4. Are any of my assumptions correct?  Am I barking up the wrong tree?

&PersistentVolumeClaim{ObjectMeta:k8s_io_apimachinery_pkg_apis_meta_v1.ObjectMeta{Name:static-files,GenerateName:,Namespace:webregistry,SelfLink:/api/v1/nam
espaces/webregistry/persistentvolumeclaims/static-files,UID:8bb48838-8eb0-11e9-832f-005056a1102f,ResourceVersion:92297070,Generation:0,CreationTimestamp:201
9-06-14 10:27:32 -0400 EDT,DeletionTimestamp:<nil>,DeletionGracePeriodSeconds:nil,Labels:map[string]string{},Annotations:map[string]string{pv.kubernetes.io/
bind-completed: yes,pv.kubernetes.io/bound-by-controller: yes,volume.beta.kubernetes.io/storage-provisioner: default,},OwnerReferences:[],Finalizers:[kubern
etes.io/pvc-protection],ClusterName:,Initializers:nil,ManagedFields:[],},Spec:PersistentVolumeClaimSpec{AccessModes:[ReadWriteOnce],Resources:ResourceRequir
ements{Limits:ResourceList{},Requests:ResourceList{storage: {{1073741824 0} {<nil>} 1Gi BinarySI},},},VolumeName:pvc-8bb48838-8eb0-11e9-832f-005056a1102f,Se
lector:nil,StorageClassName:*standard,VolumeMode:nil,DataSource:nil,},Status:PersistentVolumeClaimStatus{Phase:Bound,AccessModes:[ReadWriteOnce],Capacity:Re
sourceList{storage: {{1073741824 0} {<nil>} 1Gi BinarySI},},Conditions:[],},}

1. It is a struct, *"k8s.io/api/core/v1".PersistentVolumeClaim specifically
2. I just cheated and googled it. https://godoc.org/k8s.io/api/core/v1#PersistentVolumeClaim explains the keys in it.
3. See above
4. Your assumptions were correct.