The problem is that the package exists in the vendored folder in vendor/ and also on your $GOPATH. Vendoring "github.com/openshift/client-go" should solve your problem.

To answer your second question, for the use case you have described, not really. If you want to create an OpenShift build then yes you need to use the client as this API object does not exist in Kubernetes. If you want to simply create a Pod then you don't need the build client. A simple example for the API reference might look as follows:

package main

import (
    "k8s.io/api/core/v1"
    "k8s.io/client-go/tools/clientcmd"

    metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
    corev1client "k8s.io/client-go/kubernetes/typed/core/v1"
)

func main() {
    kubeconfig := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
        clientcmd.NewDefaultClientConfigLoadingRules(),
        &clientcmd.ConfigOverrides{},
    )
    namespace, _, err := kubeconfig.Namespace()
    if err != nil {
        panic(err)
    }
    restconfig, err := kubeconfig.ClientConfig()
    if err != nil {
        panic(err)
    }
    coreclient, err := corev1client.NewForConfig(restconfig)
    if err != nil {
        panic(err)
    }

    _, err = coreclient.Pods(namespace).Create(&v1.Pod{
        ObjectMeta: metav1.ObjectMeta{
            Name: "example",
        },
        Spec: v1.PodSpec{
            Containers: []v1.Container{
                {
                    Name:    "ubuntu",
                    Image:   "ubuntu:trusty",
                    Command: []string{"echo"},
                    Args:    []string{"Hello World"},
                },
            },
        },
    })
    if err != nil {
        panic(err)
    }

}