PING a quiet IRC listener client before closing it (closes #155)

serve closed a connection after five minutes with nothing read and never
sent a PING, so a quiet registered client lost its session. It now sends
PING :<server> after pingInterval with nothing read, and closes the
connection when nothing is read within pongDeadline after that. Every
line read starts both waits again. readTimeout is removed.

Unregistered connections are sent the PING too, so a PONG before
registration is now ignored instead of answered with ERR_NOTREGISTERED.

Model: opus-5-5

internal/ircserver/server.go

@@ -6,6 +6,7 @@ import (
 	"log/slog"
 	"net"
 	"sync"
+	"time"
 
 	"go.uber.org/fx"
 	"sneak.berlin/go/neoirc/internal/broker"
@@ -38,6 +39,11 @@ type Server struct {
 	mu       sync.Mutex
 	conns    map[*Conn]struct{}
 	cancel   context.CancelFunc
+
+	// pingInterval and pongDeadline are the constants of the
+	// same names, except in tests, which shorten them.
+	pingInterval time.Duration
+	pongDeadline time.Duration
 }
 
 // New creates a new IRC Server and registers its lifecycle
@@ -57,6 +63,9 @@ func New(
 		listener: nil,
 		cancel:   nil,
 		mu:       sync.Mutex{},
+
+		pingInterval: pingInterval,
+		pongDeadline: pongDeadline,
 	}
 
 	listenAddr := params.Config.IRCListenAddr
@@ -153,7 +162,7 @@ func (s *Server) acceptLoop(ctx context.Context) {
 				s.mu.Unlock()
 			}()
 
-			client.serve(ctx)
+			client.serve(ctx, s.pingInterval, s.pongDeadline)
 		}()
 	}
 }