Incorrect repository layour for v2 Go Modules

[jsafrane]

From kubernetes-csi/external-snapshotter#239:

$ go get -v github.com/kubernetes-csi/external-attacher@v2.1.0
go get github.com/kubernetes-csi/external-attacher@v2.1.0: github.com/kubernetes-csi/external-attacher@v2.1.0: invalid version: module contains a go.mod file, so major version must be compatible: should be v0 or v1, not v2

See kubernetes-csi/external-snapshotter#240 for a fix.

[alex1989hu]

Do you need dep compatibility with all of its side effect (e.g. symlink creation in v2 directory)?

[alex1989hu]

To verify: https://sum.golang.org/lookup/github.com/kubernetes-csi/external-attacher/v2@v2.1.1

Example go.mod

 module github.com/foo/bar

 go 1.13

 require (
     github.com/kubernetes-csi/external-attacher/v2 v2.1.1
 )

Import statements have to be updated to use it correctly:

package main

import (
	"github.com/kubernetes-csi/external-attacher/v2/pkg/controller"
)

// Your code here