$ cd go1.9/src/archive/tar
$ g tar:
common.go:205:		return nil, errors.New("tar: FileInfo is nil")
common.go:232:		return nil, fmt.Errorf("archive/tar: sockets not supported")
common.go:234:		return nil, fmt.Errorf("archive/tar: unknown file mode %v", fm)
reader.go:22:	ErrHeader = errors.New("archive/tar: invalid tar header")
writer.go:23:	ErrWriteTooLong    = errors.New("archive/tar: write too long")
writer.go:24:	ErrFieldTooLong    = errors.New("archive/tar: header field too long")
writer.go:25:	ErrWriteAfterClose = errors.New("archive/tar: write after close")
writer.go:26:	errInvalidHeader   = errors.New("archive/tar: header field too long or contains invalid values")
writer.go:51:		tw.err = fmt.Errorf("archive/tar: missed writing %d bytes", tw.nb)
$ 

$ cd ~/go/src/archive/tar
$ g tar:
common.go:31:	ErrHeader          = errors.New("tar: invalid tar header")
common.go:32:	ErrWriteTooLong    = errors.New("tar: write too long")
common.go:33:	ErrFieldTooLong    = errors.New("tar: header field too long")
common.go:34:	ErrWriteAfterClose = errors.New("tar: write after close")
common.go:35:	errMissData        = errors.New("tar: sparse file references non-existent data")
common.go:36:	errUnrefData       = errors.New("tar: sparse file contains unreferenced data")
common.go:37:	errWriteHole       = errors.New("tar: write non-NUL byte in sparse hole")
common.go:43:	const prefix = "tar: cannot encode header"
common.go:583:		return errors.New("tar: invalid sparse holes")
common.go:701:		return nil, errors.New("tar: FileInfo is nil")
common.go:728:		return nil, fmt.Errorf("tar: sockets not supported")
common.go:730:		return nil, fmt.Errorf("tar: unknown file mode %v", fm)
writer.go:56:		return fmt.Errorf("tar: missed writing %d bytes", nb)
writer_test.go:272:		//	gnutar: Substituting `.' for empty member name
writer_test.go:274:		//	gnutar: Substituting `.' for empty member name
$