  In this study, we present long term photometric variations of the close
binary system \astrobj{GO Cyg}. Modelling of the system shows that the primary
is filling Roche lobe and the secondary of the system is almost filling its
Roche lobe. The physical parameters of the system are $M_1 = 3.0\pm0.2
M_{\odot}$, $M_2 = 1.3 \pm 0.1 M_{\odot}$, $R_1 = 2.50\pm 0.12 R_{\odot}$, $R_2
= 1.75 \pm 0.09 R_{\odot}$, $L_1 = 64\pm 9 L_{\odot}$, $L_2 = 4.9 \pm 0.7
L_{\odot}$, and $a = 5.5 \pm 0.3 R_{\odot}$. Our results show that \astrobj{GO
Cyg} is the most massive system near contact binary (NCB). Analysis of times of
the minima shows a sinusoidal variation with a period of $92.3\pm0.5$ years due
to a third body whose mass is less than 2.3$M_{\odot}$. Finally a period
variation rate of $-1.4\times10^{-9}$ d/yr has been determined using all
available light curves.
