-- input --
[math] is a package but this is not a doc link.

[io] is a doc link.

[math]: https://example.com
-- gofmt --
[math] is a package but this is not a doc link.

[io] is a doc link.

[math]: https://example.com
-- text --
math is a package but this is not a doc link.

io is a doc link.

[math]: https://example.com
-- markdown --
[math](https://example.com) is a package but this is not a doc link.

[io](/io) is a doc link.
-- html --
<p><a href="https://example.com">math</a> is a package but this is not a doc link.
<p><a href="/io">io</a> is a doc link.