Remove gopkg.in/tomb.v2 dependency

`gopkg.in/tomb.v2` is inactive for long time and incus use less function of it.

Signed-off-by: JUN JIE NAN <[email protected]>

Author: nanjj

go.mod

@@ -61,7 +61,6 @@ require (
 	golang.org/x/text v0.24.0
 	golang.org/x/tools v0.32.0
 	google.golang.org/protobuf v1.36.6
-	gopkg.in/tomb.v2 v2.0.0-20161208151619-d5d1b5820637
 	gopkg.in/yaml.v2 v2.4.0
 	k8s.io/utils v0.0.0-20250321185631-1f6e0b77f77e
 )

go.sum

@@ -919,8 +919,6 @@ gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntN
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
 gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
 gopkg.in/ini.v1 v1.62.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=
-gopkg.in/tomb.v2 v2.0.0-20161208151619-d5d1b5820637 h1:yiW+nvdHb9LVqSHQBXfZCieqV4fzYhNBql77zY0ykqs=
-gopkg.in/tomb.v2 v2.0.0-20161208151619-d5d1b5820637/go.mod h1:BHsqpu/nsuzkT5BpiH1EMZPLyqSMM8JbIavyFACoFNk=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.3/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.8/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=

internal/server/endpoints/endpoints.go

@@ -5,10 +5,9 @@ import (
 	"net"
 	"net/http"
 	"sync"
+	"sync/atomic"
 	"time"
 
-	tomb "gopkg.in/tomb.v2"
-
 	"github.com/lxc/incus/v6/internal/linux"
 	"github.com/lxc/incus/v6/internal/server/endpoints/listeners"
 	"github.com/lxc/incus/v6/internal/util"
@@ -157,7 +156,7 @@ func Up(config *Config) (*Endpoints, error) {
 // Endpoints are in charge of bringing up and down the HTTP endpoints for
 // serving the REST API.
 type Endpoints struct {
-	tomb      *tomb.Tomb            // Controls the HTTP servers shutdown.
+	tomb      *Tomb                 // Controls the HTTP servers shutdown.
 	mu        sync.RWMutex          // Serialize access to internal state.
 	listeners map[kind]net.Listener // Activer listeners by endpoint type.
 	servers   map[kind]*http.Server // HTTP servers by endpoint type.
@@ -425,7 +424,7 @@ func (e *Endpoints) serve(kind kind) {
 	// Defer the creation of the tomb, so Down() doesn't wait on it unless
 	// we actually have spawned at least a server.
 	if e.tomb == nil {
-		e.tomb = &tomb.Tomb{}
+		e.tomb = &Tomb{}
 	}
 
 	e.tomb.Go(func() error {
@@ -501,3 +500,50 @@ var descriptions = map[kind]string{
 	vmvsock:        "VM socket",
 	storageBuckets: "Storage buckets socket",
 }
+
+// Tomb tracks the lifecycle of one or more goroutines.
+type Tomb struct {
+	count   atomic.Int32
+	wg      sync.WaitGroup
+	errOnce sync.Once
+	err     error
+}
+
+func (g *Tomb) add(delta int) {
+	g.wg.Add(delta)
+	g.count.Add(int32(delta))
+}
+
+// Go runs f in a new goroutine and tracks its termination.
+func (g *Tomb) Go(f func() error) {
+	g.add(1)
+
+	go func() {
+		defer g.add(-1)
+		if err := f(); err != nil {
+			g.errOnce.Do(func() {
+				g.err = err
+			})
+		}
+	}()
+}
+
+// Kill marks all running goroutings done.
+func (g *Tomb) Kill(err error) {
+	if err != nil {
+		g.errOnce.Do(func() {
+			g.err = err
+		})
+	}
+
+	c := int(g.count.Load())
+	if c > 0 {
+		g.add(-c)
+	}
+}
+
+// Wait blocks until all goroutines have finished running.
+func (g *Tomb) Wait() error {
+	g.wg.Wait()
+	return g.err
+}