we need option to execlude some packages

[sijms]

I have medium project which import small packages i made and also import: golang.org/x/text
I need to cancel golang.org/x/text from obfuscation to accelerate the operation.
after searching in the code i found that when you transfer package to $GOROOT it will not include
in the obfuscation but I receive error from function
func interfaceMethods(gopath string) (map[string]bool, error){}
cannot import golang.org/x/tools/go/ssa/ssautil

I temporary solve the problem by write continue when the program cannot import a package because actually
this package I am not using and I didn't need to obfuscate it

pkg, err := ctx.Import(pkgName, gopath, 0)
if err != nil {
continue
//return nil, fmt.Errorf("import %s: %s", pkgName, err)
}