code: func New(ctxt *build.Context, fset *token.FileSet, packages map[string]*types.Package) *Importer {
  	return &Importer{
  		ctxt:     ctxt,
  		fset:     fset,
  		sizes:    types.SizesFor(ctxt.Compiler, ctxt.GOARCH), // uses go/types default if GOARCH not found
  		packages: packages,
  	}
  }
docs: // NewImporter returns a new Importer for the given context, file set, and map
  // of packages. The context is used to resolve import paths to package paths,
  // and identifying the files belonging to the package. If the context provides
  // non-nil file system functions, they are used instead of the regular package
  // os functions. The file set is used to track position information of package
  // files; and imported packages are added to the packages map.