all: gofmt -w -s (simplify) tests

And it updates the build tag style on a couple files.

Change-Id: I84478d822c8de3f84b56fa1176c99d2ea5083237
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

wgengine/magicsock/magicsock_test.go

@@ -401,14 +401,14 @@ func TestPickDERPFallback(t *testing.T) {
 	c := newConn()
 	dm := &tailcfg.DERPMap{
 		Regions: map[int]*tailcfg.DERPRegion{
-			1: &tailcfg.DERPRegion{},
-			2: &tailcfg.DERPRegion{},
-			3: &tailcfg.DERPRegion{},
-			4: &tailcfg.DERPRegion{},
-			5: &tailcfg.DERPRegion{},
-			6: &tailcfg.DERPRegion{},
-			7: &tailcfg.DERPRegion{},
-			8: &tailcfg.DERPRegion{},
+			1: {},
+			2: {},
+			3: {},
+			4: {},
+			5: {},
+			6: {},
+			7: {},
+			8: {},
 		},
 	}
 	c.derpMap = dm
@@ -1011,7 +1011,7 @@ func testTwoDevicePing(t *testing.T, d *devices) {
 		PrivateKey: m1.privateKey,
 		Addresses:  []netaddr.IPPrefix{netaddr.MustParseIPPrefix("1.0.0.1/32")},
 		Peers: []wgcfg.Peer{
-			wgcfg.Peer{
+			{
 				PublicKey:  m2.privateKey.Public(),
 				DiscoKey:   m2.conn.DiscoPublicKey(),
 				AllowedIPs: []netaddr.IPPrefix{netaddr.MustParseIPPrefix("1.0.0.2/32")},
@@ -1023,7 +1023,7 @@ func testTwoDevicePing(t *testing.T, d *devices) {
 		PrivateKey: m2.privateKey,
 		Addresses:  []netaddr.IPPrefix{netaddr.MustParseIPPrefix("1.0.0.2/32")},
 		Peers: []wgcfg.Peer{
-			wgcfg.Peer{
+			{
 				PublicKey:  m1.privateKey.Public(),
 				DiscoKey:   m1.conn.DiscoPublicKey(),
 				AllowedIPs: []netaddr.IPPrefix{netaddr.MustParseIPPrefix("1.0.0.1/32")},

wgengine/userspace_test.go

@@ -99,7 +99,7 @@ func TestUserspaceEngineReconfig(t *testing.T) {
 	} {
 		nm := &netmap.NetworkMap{
 			Peers: []*tailcfg.Node{
-				&tailcfg.Node{
+				{
 					Key: nkFromHex(nodeHex),
 				},
 			},

wgengine/winnet/winnet.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build windows
 // +build windows
 
 package winnet