The proxy can't actively disconnect, you need to use socket shutdown instead of directly close

common/conn/conn.go

@@ -45,14 +45,41 @@ func Relay(left, right net.Conn) (int64, int64, error) {
 
 	go func() {
 		n, err := io.Copy(right, left)
-		right.SetDeadline(time.Now()) // wake up the other goroutine blocking on right
-		left.SetDeadline(time.Now())  // wake up the other goroutine blocking on left
+
+		switch src := left.(type) {
+		case *net.TCPConn:
+			src.CloseRead()
+		default:
+			src.SetDeadline(time.Now())
+		}
+
+		switch dst := right.(type) {
+		case *net.TCPConn:
+			dst.CloseWrite()
+			dst.SetDeadline(time.Now().Add(time.Second * 60))
+		default:
+			dst.SetDeadline(time.Now())
+		}
+
 		ch <- res{n, err}
 	}()
 
 	n, err := io.Copy(left, right)
-	right.SetDeadline(time.Now()) // wake up the other goroutine blocking on right
-	left.SetDeadline(time.Now())  // wake up the other goroutine blocking on left
+	switch src := left.(type) {
+	case *net.TCPConn:
+		src.CloseWrite()
+		src.SetDeadline(time.Now().Add(time.Second * 60))
+	default:
+		src.SetDeadline(time.Now())
+	}
+
+	switch dst := right.(type) {
+	case *net.TCPConn:
+		dst.CloseRead()
+	default:
+		dst.SetDeadline(time.Now())
+	}
+
 	rs := <-ch
 
 	if err == nil {