fix: change string `/` with `os.PathSeparator`

[ahmadkarlam]

This PR will be fix error path separator on windows.

When I am using repogen, I found error unable to load env file.

I asked a friend because I was afraid that I would make a mistake when using repogen. It turned out that my friend and I used the same command.

I did some debugging and it turned out that when repogen did strings.Split, the windows path with unix was different.

That's why I changed "/" to os.PathSeparator to handle multiplatform for this command.