refactor: replace Get/Set patterns with idiomatic Go interfaces

- rename constructors to New
- remove Get/Set-style accessors
- replace string-based enums with iota-backed types

session/forwarder/forwarder.go

@@ -30,50 +30,50 @@ func copyWithBuffer(dst io.Writer, src io.Reader) (written int64, err error) {
 	return io.CopyBuffer(dst, src, buf)
 }
 
-type Forwarder struct {
+type forwarder struct {
 	listener      net.Listener
 	tunnelType    types.TunnelType
 	forwardedPort uint16
-	slugManager   slug.Manager
+	slug          slug.Slug
 	lifecycle     Lifecycle
 }
 
-func NewForwarder(slugManager slug.Manager) *Forwarder {
-	return &Forwarder{
+func New(slug slug.Slug) Forwarder {
+	return &forwarder{
 		listener:      nil,
-		tunnelType:    "",
+		tunnelType:    types.UNKNOWN,
 		forwardedPort: 0,
-		slugManager:   slugManager,
+		slug:          slug,
 		lifecycle:     nil,
 	}
 }
 
 type Lifecycle interface {
-	GetConnection() ssh.Conn
+	Connection() ssh.Conn
 }
 
-type ForwardingController interface {
-	AcceptTCPConnections()
+type Forwarder interface {
 	SetType(tunnelType types.TunnelType)
-	GetTunnelType() types.TunnelType
-	GetForwardedPort() uint16
+	SetLifecycle(lifecycle Lifecycle)
 	SetForwardedPort(port uint16)
 	SetListener(listener net.Listener)
-	GetListener() net.Listener
-	Close() error
+	Listener() net.Listener
+	TunnelType() types.TunnelType
+	ForwardedPort() uint16
 	HandleConnection(dst io.ReadWriter, src ssh.Channel, remoteAddr net.Addr)
-	SetLifecycle(lifecycle Lifecycle)
 	CreateForwardedTCPIPPayload(origin net.Addr) []byte
 	WriteBadGatewayResponse(dst io.Writer)
+	AcceptTCPConnections()
+	Close() error
 }
 
-func (f *Forwarder) SetLifecycle(lifecycle Lifecycle) {
+func (f *forwarder) SetLifecycle(lifecycle Lifecycle) {
 	f.lifecycle = lifecycle
 }
 
-func (f *Forwarder) AcceptTCPConnections() {
+func (f *forwarder) AcceptTCPConnections() {
 	for {
-		conn, err := f.GetListener().Accept()
+		conn, err := f.Listener().Accept()
 		if err != nil {
 			if errors.Is(err, net.ErrClosed) {
 				return
@@ -100,7 +100,7 @@ func (f *Forwarder) AcceptTCPConnections() {
 		resultChan := make(chan channelResult, 1)
 
 		go func() {
-			channel, reqs, err := f.lifecycle.GetConnection().OpenChannel("forwarded-tcpip", payload)
+			channel, reqs, err := f.lifecycle.Connection().OpenChannel("forwarded-tcpip", payload)
 			resultChan <- channelResult{channel, reqs, err}
 		}()
 
@@ -130,7 +130,7 @@ func (f *Forwarder) AcceptTCPConnections() {
 	}
 }
 
-func (f *Forwarder) HandleConnection(dst io.ReadWriter, src ssh.Channel, remoteAddr net.Addr) {
+func (f *forwarder) HandleConnection(dst io.ReadWriter, src ssh.Channel, remoteAddr net.Addr) {
 	defer func() {
 		_, err := io.Copy(io.Discard, src)
 		if err != nil {
@@ -174,31 +174,31 @@ func (f *Forwarder) HandleConnection(dst io.ReadWriter, src ssh.Channel, remoteA
 	wg.Wait()
 }
 
-func (f *Forwarder) SetType(tunnelType types.TunnelType) {
+func (f *forwarder) SetType(tunnelType types.TunnelType) {
 	f.tunnelType = tunnelType
 }
 
-func (f *Forwarder) GetTunnelType() types.TunnelType {
+func (f *forwarder) TunnelType() types.TunnelType {
 	return f.tunnelType
 }
 
-func (f *Forwarder) GetForwardedPort() uint16 {
+func (f *forwarder) ForwardedPort() uint16 {
 	return f.forwardedPort
 }
 
-func (f *Forwarder) SetForwardedPort(port uint16) {
+func (f *forwarder) SetForwardedPort(port uint16) {
 	f.forwardedPort = port
 }
 
-func (f *Forwarder) SetListener(listener net.Listener) {
+func (f *forwarder) SetListener(listener net.Listener) {
 	f.listener = listener
 }
 
-func (f *Forwarder) GetListener() net.Listener {
+func (f *forwarder) Listener() net.Listener {
 	return f.listener
 }
 
-func (f *Forwarder) WriteBadGatewayResponse(dst io.Writer) {
+func (f *forwarder) WriteBadGatewayResponse(dst io.Writer) {
 	_, err := dst.Write(types.BadGatewayResponse)
 	if err != nil {
 		log.Printf("failed to write Bad Gateway response: %v", err)
@@ -206,20 +206,20 @@ func (f *Forwarder) WriteBadGatewayResponse(dst io.Writer) {
 	}
 }
 
-func (f *Forwarder) Close() error {
-	if f.GetListener() != nil {
+func (f *forwarder) Close() error {
+	if f.Listener() != nil {
 		return f.listener.Close()
 	}
 	return nil
 }
 
-func (f *Forwarder) CreateForwardedTCPIPPayload(origin net.Addr) []byte {
+func (f *forwarder) CreateForwardedTCPIPPayload(origin net.Addr) []byte {
 	var buf bytes.Buffer
 
 	host, originPort := parseAddr(origin.String())
 
 	writeSSHString(&buf, "localhost")
-	err := binary.Write(&buf, binary.BigEndian, uint32(f.GetForwardedPort()))
+	err := binary.Write(&buf, binary.BigEndian, uint32(f.ForwardedPort()))
 	if err != nil {
 		log.Printf("Failed to write string to buffer: %v", err)
 		return nil