Also add information on how to contact you by electronic and paper mail.

  If your software can interact with users remotely through a computer
network, you should also make sure that it provides a way for users to
get its source.  For example, if your program is a web application, its
interface could display a "Source" link that leads users to an archive
of the code.  There are many ways you could offer source, and different

pkg os/user, func Current() (*User, error)
pkg os/user, func Lookup(string) (*User, error)
pkg os/user, func LookupId(string) (*User, error)
pkg os/user, method (UnknownUserError) Error() string
pkg os/user, method (UnknownUserIdError) Error() string
pkg os/user, type UnknownUserError string
pkg os/user, type UnknownUserIdError int
pkg os/user, type User struct