Added SetIdleClose

It's now possible to automatically close idle connections by
calling the SetIdleClose method.

    s := redcon.NewServer(...)
    s.SetIdleClose(time.Minute*5)
    s.ListenAndServe()

closed #34

redcon.go

@@ -10,6 +10,7 @@ import (
 	"net"
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/tidwall/btree"
 	"github.com/tidwall/match"
@@ -356,6 +357,7 @@ func serve(s *Server) error {
 			rd:   NewReader(lnconn),
 		}
 		s.mu.Lock()
+		c.idleClose = s.idleClose
 		s.conns[c] = true
 		s.mu.Unlock()
 		if s.accept != nil && !s.accept(c) {
@@ -395,6 +397,9 @@ func handle(s *Server, c *conn) {
 		// read commands and feed back to the client
 		for {
 			// read pipeline commands
+			if c.idleClose != 0 {
+				c.conn.SetReadDeadline(time.Now().Add(c.idleClose))
+			}
 			cmds, err := c.rd.readCommands(nil)
 			if err != nil {
 				if err, ok := err.(*errProtocol); ok {
@@ -439,6 +444,7 @@ type conn struct {
 	detached  bool
 	closed    bool
 	cmds      []Command
+	idleClose time.Duration
 }
 
 func (c *conn) Close() error {
@@ -550,6 +556,7 @@ type Server struct {
 	conns     map[*conn]bool
 	ln        net.Listener
 	done      bool
+	idleClose time.Duration
 
 	// AcceptError is an optional function used to handle Accept errors.
 	AcceptError func(err error)
@@ -1346,3 +1353,11 @@ func (ps *PubSub) unsubscribe(conn Conn, pattern, all bool, channel string) {
 	}
 	sconn.dconn.Flush()
 }
+
+// SetIdleClose will automatically close idle connections after the specified
+// duration. Use zero to disable this feature.
+func (s *Server) SetIdleClose(dur time.Duration) {
+	s.mu.Lock()
+	s.idleClose = dur
+	s.mu.Unlock()
+}