chore: remove dependency on /x/sync

For a public repo it's better with one less dependency than a slightly
simpler test in this case.

go.mod

@@ -4,6 +4,5 @@ go 1.14
 
 require (
 	golang.org/x/net v0.0.0-20201224014010-6772e930b67b
-	golang.org/x/sync v0.0.0-20201207232520-09787c993a3a
 	gotest.tools/v3 v3.0.3
 )

go.sum

@@ -9,8 +9,6 @@ golang.org/x/net v0.0.0-20201224014010-6772e930b67b h1:iFwSg7t5GZmB/Q5TjiEAsdoLD
 golang.org/x/net v0.0.0-20201224014010-6772e930b67b/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58 h1:8gQV6CLnAEikrhgkHFbMAEhagSSnXWGV915qUMm9mrU=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20201207232520-09787c993a3a h1:DcqTD9SDLc+1P/r1EmRBwnVsrOwW+kk2vWf9n+1sGhs=
-golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a h1:1BGLXjeY4akVXGgbC9HugT3Jv3hCI0z56oJR5vAMgBU=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68 h1:nxC68pudNYkKU6jWhgrqdreuFiOQWj1Fs7T3VrH4Pjw=

receiver_test.go

@@ -3,11 +3,11 @@ package vlp16
 import (
 	"context"
 	"net"
+	"sync"
 	"testing"
 	"time"
 
 	"golang.org/x/net/nettest"
-	"golang.org/x/sync/errgroup"
 	"gotest.tools/v3/assert"
 )
 
@@ -18,16 +18,20 @@ func TestClient_Receive(t *testing.T) {
 	addr := getFreeAddress(t)
 	rx, err := ListenUDP(ctx, addr)
 	assert.NilError(t, err)
-	var g errgroup.Group
-	g.Go(func() error {
-		return rx.Receive(ctx)
-	})
+	var g sync.WaitGroup
+	g.Add(1)
+	go func() {
+		defer g.Done()
+		if err := rx.Receive(ctx); err != nil {
+			t.Error(err)
+		}
+	}()
 	conn, err := net.Dial("udp4", addr)
 	assert.NilError(t, err)
 	_, err = conn.Write(exampleRawPacket(t)[:])
 	assert.NilError(t, err)
 	assert.NilError(t, conn.Close())
-	assert.NilError(t, g.Wait())
+	g.Wait()
 	assert.DeepEqual(t, exampleRawPacket(t), rx.RawPacket())
 	assert.DeepEqual(t, examplePacket(), rx.Packet())
 }