stdPackages: stdPackages,
			importMap:   importMap,
			importDir:   importDir,
		}
		imports, _ = listCache.LoadOrStore(name, imports)
	}

	li := imports.(listImports)
	w.stdPackages = li.stdPackages
	w.importDir = li.importDir
	w.importMap = li.importMap
}

// listEnv returns the process environment to use when invoking 'go list' for
// the given context.
func listEnv(c *build.Context) []string {