fix package paths on windows

[jon-walton]

Hello,

I wasn't able to run gqlgen on windows due to a rather cryptic error:

cannot find package "C:\\Users\\jonwa\\go\\src\\gitlab.com\\***\\backend\\dashboard\\internal\\graph" in any of:
	C:\Users\jonwa\go\src\gitlab.com\***\vendor\C:\Users\jonwa\go\src\gitlab.com\***\backend\dashboard\internal\graph (vendor tree)
	C:\Go\src\C:\Users\jonwa\go\src\gitlab.com\***\backend\dashboard\internal\graph (from $GOROOT)
	C:\Users\jonwa\go\src\C:\Users\jonwa\go\src\gitlab.com\***\backend\dashboard\internal\graph (from $GOPATH)
failed to generate code: couldn't load packages due to errors: C:\Users\jonwa\go\src\gitlab.com\***\backend\dashboard\internal\graph
rootResolver.go:1: running "gorunpkg": exit status 1

Process finished with exit code 1

this was due to the gopath splitting using unix separators and gopath += "/src/" resulted in gopath being set to c:\Users\jonwa\go/src/ so the package name didn't get set correctly.

not sure what you want to do with the error. it's rather cryptic (passed straight from go's loader) but once you remember the package is gitlab.com\\***\\backend\\dashboard\\internal\\graph and not C:\\Users\\jonwa\\go\\src\\gitlab.com\\***\\backend\\dashboard\\internal\\graph it makes sense

[vektah]

Thanks for the pr, I've tried to stick to windows compatible methods, but really should find a windows ci host to make sure these kind of breaks don't happen.

I think in this case the error message is fine, if gqlgen was generating paths correctly it would be what the user did wrong