code: func allPackages(pattern string) []string {
  	pkgs := matchPackages(pattern)
  	if len(pkgs) == 0 {
  		fmt.Fprintf(os.Stderr, "warning: %q matched no packages\n", pattern)
  	}
  	return pkgs
  }
docs: // allPackages returns all the packages that can be found
  // under the $GOPATH directories and $GOROOT matching pattern.
  // The pattern is either "all" (all packages), "std" (standard packages)
  // or a path including "...".