Difficult change of colum’s name in DataFrame in Python Pandas?

I have DataFrame like below:

df - pd.DataFrame({"col1" : (1 ,2 ,3),
                   "col1" : (2,3,4),
                   "col2" : (10, 11, 12)})

And then I make: df.columns.tolist() and I have list of columns of df:

("col1",
 "col1",
 "col2)

And how can I change the name of the second “col1” to for example “col3” ? because as I means if I will try: df.rename(columns={"col1" : "col3"}, inplace=True) the first “col1” will be changed.