update kubectl-pg plugin

[FxKu]

• move to Go 1.15
• update Go modules
• add context field for Api calls

go mod vendor currently fails for me with:

GO111MODULE=on go mod tidy  
go: finding module for package k8s.io/api/auditregistration/v1alpha1
go: finding module for package github.com/googleapis/gnostic/OpenAPIv2
github.com/zalando/postgres-operator/kubectl-pg/cmd imports
	k8s.io/client-go/kubernetes imports
	k8s.io/client-go/discovery imports
	github.com/googleapis/gnostic/OpenAPIv2: module github.com/googleapis/gnostic@latest found (v0.5.3), but does not contain package github.com/googleapis/gnostic/OpenAPIv2
github.com/zalando/postgres-operator/kubectl-pg/cmd imports
	k8s.io/client-go/kubernetes imports
	k8s.io/client-go/kubernetes/typed/auditregistration/v1alpha1 imports
	k8s.io/api/auditregistration/v1alpha1: module k8s.io/api@latest found (v0.20.0), but does not contain package k8s.io/api/auditregistration/v1alpha1

Edit: Seems the v1.6.0 operator release was necessary to fix this.

[sdudoladov]

👍

[FxKu]

👍