Using symbolic subs in for loop

Hi,

I have the following equation:

syms tf zeta taum tgo
eq = (exp(-tgo/taum)+tgo/taum-1)^2;
INT = int(eq,tgo);

TauM = 5;
dt = 0.01;

Tgo = 10;
for Tgo > 0

INT = double(subs(INT,{tgo,taum},{Tgo,TauM}));

Tgo = Tgo - dt

end

My question is: using subs inside the for loop slows it down. Is there anyway to make it faster? (The problem is Tgo is dynamic).

P.s. In this example I could write the integral not a syms however in many problems I would like to insert the function and run the code and not to do all the work before.

Thank you.