lib: Move to go modules and shed a few tears

The old system with vendor/ and git submodules worked great,
unfortunately FUD around git submodules seemed to scare people away and
golang moved to a go.mod system that adds a new lock file format instead
of using the built-in git version. It's now almost impossible to use
modern golang without this, so we've switched.

So much for the golang compatibility promise-- turns out it doesn't
apply to the useful parts that I actually care about like this.

Thanks to frebib for his incredibly valuable contributions to this
patch. This snide commit message is mine alone.

This patch also mixes in some changes due to legacy golang as we've also
bumped the minimum version to 1.16 in the docs and tests.

Lastly, we had to disable some tests and fix up a few other misc things
to get this passing. We've definitely hot bugs in the go.mod system, and
our Makefile tries to workaround those.

etcd/callback.go

@@ -26,8 +26,8 @@ import (
 	"github.com/purpleidea/mgmt/util"
 	"github.com/purpleidea/mgmt/util/errwrap"
 
-	etcd "go.etcd.io/etcd/clientv3" // "clientv3"
-	pb "go.etcd.io/etcd/etcdserver/etcdserverpb"
+	pb "go.etcd.io/etcd/api/v3/etcdserverpb"
+	etcd "go.etcd.io/etcd/client/v3"
 )
 
 // nominateApply applies the changed watcher data onto our local caches.

etcd/chooser/chooser.go

@@ -22,7 +22,7 @@ import (
 
 	"github.com/purpleidea/mgmt/etcd/interfaces"
 
-	etcdtypes "go.etcd.io/etcd/pkg/types"
+	etcdtypes "go.etcd.io/etcd/client/pkg/v3/types"
 )
 
 // Data represents the input data that is passed to the chooser.

etcd/chooser/dynamicsize.go

@@ -25,8 +25,8 @@ import (
 
 	"github.com/purpleidea/mgmt/etcd/interfaces"
 
-	etcd "go.etcd.io/etcd/clientv3"
-	etcdtypes "go.etcd.io/etcd/pkg/types"
+	etcdtypes "go.etcd.io/etcd/client/pkg/v3/types"
+	etcd "go.etcd.io/etcd/client/v3"
 )
 
 // XXX: Test causing cluster shutdowns with:

etcd/client/resources/resources.go

@@ -27,7 +27,7 @@ import (
 	"github.com/purpleidea/mgmt/etcd/interfaces"
 	"github.com/purpleidea/mgmt/util"
 
-	etcd "go.etcd.io/etcd/clientv3"
+	etcd "go.etcd.io/etcd/client/v3"
 )
 
 const (

etcd/client/simple.go

@@ -26,8 +26,8 @@ import (
 	"github.com/purpleidea/mgmt/etcd/interfaces"
 	"github.com/purpleidea/mgmt/util/errwrap"
 
-	etcd "go.etcd.io/etcd/clientv3" // "clientv3"
-	"go.etcd.io/etcd/clientv3/namespace"
+	etcd "go.etcd.io/etcd/client/v3"
+	"go.etcd.io/etcd/client/v3/namespace"
 )
 
 // method represents the method we used to build the simple client.
@@ -301,7 +301,7 @@ func (obj *Simple) Get(ctx context.Context, path string, opts ...etcd.OpOption)
 		return nil, fmt.Errorf("empty response")
 	}
 
-	// TODO: write a resp.ToMap() function on https://godoc.org/github.com/etcd-io/etcd/etcdserver/etcdserverpb#RangeResponse
+	// TODO: write a resp.ToMap() function on https://godoc.org/github.com/etcd-io/etcd/api/etcdserverpb#RangeResponse
 	result := make(map[string]string)
 	for _, x := range resp.Kvs {
 		result[string(x.Key)] = string(x.Value)

etcd/client/str/str.go

@@ -24,8 +24,8 @@ import (
 	"github.com/purpleidea/mgmt/etcd/interfaces"
 	"github.com/purpleidea/mgmt/util/errwrap"
 
-	etcd "go.etcd.io/etcd/clientv3"
-	etcdutil "go.etcd.io/etcd/clientv3/clientv3util"
+	etcd "go.etcd.io/etcd/client/v3"
+	etcdutil "go.etcd.io/etcd/client/v3/clientv3util"
 )
 
 const (

etcd/client/strmap/strmap.go

@@ -26,8 +26,8 @@ import (
 	"github.com/purpleidea/mgmt/util"
 	"github.com/purpleidea/mgmt/util/errwrap"
 
-	etcd "go.etcd.io/etcd/clientv3"
-	etcdutil "go.etcd.io/etcd/clientv3/clientv3util"
+	etcd "go.etcd.io/etcd/client/v3"
+	etcdutil "go.etcd.io/etcd/client/v3/clientv3util"
 )
 
 const (

etcd/converger.go

@@ -23,7 +23,7 @@ import (
 
 	"github.com/purpleidea/mgmt/util/errwrap"
 
-	etcd "go.etcd.io/etcd/clientv3"
+	etcd "go.etcd.io/etcd/client/v3"
 )
 
 // setHostnameConverged sets whether a specific hostname is converged.

etcd/deployer/deployer.go

@@ -27,8 +27,8 @@ import (
 	"github.com/purpleidea/mgmt/etcd/interfaces"
 	"github.com/purpleidea/mgmt/util/errwrap"
 
-	etcd "go.etcd.io/etcd/clientv3"
-	etcdutil "go.etcd.io/etcd/clientv3/clientv3util"
+	etcd "go.etcd.io/etcd/client/v3"
+	etcdutil "go.etcd.io/etcd/client/v3/clientv3util"
 )
 
 const (

etcd/etcd.go

@@ -122,11 +122,11 @@ import (
 	"github.com/purpleidea/mgmt/util"
 	"github.com/purpleidea/mgmt/util/errwrap"
 
-	etcd "go.etcd.io/etcd/clientv3" // "clientv3"
-	"go.etcd.io/etcd/clientv3/concurrency"
-	"go.etcd.io/etcd/clientv3/namespace"
-	"go.etcd.io/etcd/embed"
-	etcdtypes "go.etcd.io/etcd/pkg/types"
+	etcdtypes "go.etcd.io/etcd/client/pkg/v3/types"
+	etcd "go.etcd.io/etcd/client/v3"
+	"go.etcd.io/etcd/client/v3/concurrency"
+	"go.etcd.io/etcd/client/v3/namespace"
+	"go.etcd.io/etcd/server/v3/embed"
 )
 
 const (

etcd/fs/file.go

@@ -30,8 +30,8 @@ import (
 
 	"github.com/purpleidea/mgmt/util/errwrap"
 
-	etcd "go.etcd.io/etcd/clientv3" // "clientv3"
-	etcdutil "go.etcd.io/etcd/clientv3/clientv3util"
+	etcd "go.etcd.io/etcd/client/v3"
+	etcdutil "go.etcd.io/etcd/client/v3/clientv3util"
 )
 
 func init() {

etcd/fs/fs.go

@@ -38,8 +38,8 @@ import (
 	"github.com/purpleidea/mgmt/util/errwrap"
 
 	"github.com/spf13/afero"
-	etcd "go.etcd.io/etcd/clientv3" // "clientv3"
-	rpctypes "go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes"
+	rpctypes "go.etcd.io/etcd/api/v3/v3rpc/rpctypes"
+	etcd "go.etcd.io/etcd/client/v3"
 )
 
 func init() {

etcd/helpers.go

@@ -27,10 +27,10 @@ import (
 	"github.com/purpleidea/mgmt/util"
 	"github.com/purpleidea/mgmt/util/errwrap"
 
-	etcd "go.etcd.io/etcd/clientv3"
-	pb "go.etcd.io/etcd/etcdserver/etcdserverpb"
-	"go.etcd.io/etcd/mvcc/mvccpb"
-	etcdtypes "go.etcd.io/etcd/pkg/types" // generated package
+	pb "go.etcd.io/etcd/api/v3/etcdserverpb"
+	"go.etcd.io/etcd/api/v3/mvccpb"
+	etcdtypes "go.etcd.io/etcd/client/pkg/v3/types" // generated package
+	etcd "go.etcd.io/etcd/client/v3"
 )
 
 // setEndpoints sets the endpoints on the etcd client if it exists. It

etcd/interfaces/client.go

@@ -20,8 +20,8 @@ package interfaces
 import (
 	"context"
 
-	etcd "go.etcd.io/etcd/clientv3" // "clientv3"
-	pb "go.etcd.io/etcd/etcdserver/etcdserverpb"
+	pb "go.etcd.io/etcd/api/v3/etcdserverpb"
+	etcd "go.etcd.io/etcd/client/v3"
 )
 
 // WatcherData is the structure of data passed to a callback from any watcher.

etcd/membership.go

@@ -26,10 +26,10 @@ import (
 
 	"github.com/purpleidea/mgmt/util/errwrap"
 
-	etcd "go.etcd.io/etcd/clientv3"
-	rpctypes "go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes"
-	pb "go.etcd.io/etcd/etcdserver/etcdserverpb"
-	etcdtypes "go.etcd.io/etcd/pkg/types"
+	pb "go.etcd.io/etcd/api/v3/etcdserverpb"
+	rpctypes "go.etcd.io/etcd/api/v3/v3rpc/rpctypes"
+	etcdtypes "go.etcd.io/etcd/client/pkg/v3/types"
+	etcd "go.etcd.io/etcd/client/v3"
 )
 
 // addSelfState is used to populate the initial state when I am adding myself.

etcd/methods.go

@@ -24,9 +24,9 @@ import (
 
 	"github.com/purpleidea/mgmt/util/errwrap"
 
-	etcd "go.etcd.io/etcd/clientv3"
-	etcdutil "go.etcd.io/etcd/clientv3/clientv3util"
-	etcdtypes "go.etcd.io/etcd/pkg/types"
+	etcdtypes "go.etcd.io/etcd/client/pkg/v3/types"
+	etcd "go.etcd.io/etcd/client/v3"
+	etcdutil "go.etcd.io/etcd/client/v3/clientv3util"
 )
 
 // volunteer offers yourself up to be a server if needed. If you specify a nil

etcd/scheduler/scheduler.go

@@ -28,8 +28,8 @@ import (
 
 	"github.com/purpleidea/mgmt/util/errwrap"
 
-	etcd "go.etcd.io/etcd/clientv3"
-	"go.etcd.io/etcd/clientv3/concurrency"
+	etcd "go.etcd.io/etcd/client/v3"
+	"go.etcd.io/etcd/client/v3/concurrency"
 )
 
 const (

etcd/server.go

@@ -27,8 +27,9 @@ import (
 	"github.com/purpleidea/mgmt/util"
 	"github.com/purpleidea/mgmt/util/errwrap"
 
-	"go.etcd.io/etcd/embed"
-	etcdtypes "go.etcd.io/etcd/pkg/types"
+	etcdTransport "go.etcd.io/etcd/client/pkg/v3/transport"
+	etcdtypes "go.etcd.io/etcd/client/pkg/v3/types"
+	"go.etcd.io/etcd/server/v3/embed"
 )
 
 const (
@@ -149,6 +150,11 @@ func (obj *EmbdEtcd) runServer(newCluster bool, peerURLsMap etcdtypes.URLsMap) (
 	//cfg.LogOutputs = []string{} // FIXME: add a way to pass in our logf func
 	cfg.LogLevel = "error" // keep things quieter for now
 
+	cfg.SocketOpts = etcdTransport.SocketOpts{
+		//ReusePort: false, // SO_REUSEPORT
+		ReuseAddress: true, // SO_REUSEADDR
+	}
+
 	cfg.InitialCluster = initialPeerURLsMap.String() // including myself!
 	if newCluster {
 		cfg.ClusterState = embed.ClusterStateFlagNew

etcd/util.go

@@ -26,7 +26,7 @@ import (
 
 	"github.com/purpleidea/mgmt/util/errwrap"
 
-	etcdtypes "go.etcd.io/etcd/pkg/types"
+	etcdtypes "go.etcd.io/etcd/client/pkg/v3/types"
 )
 
 // copyURL copies a URL.