Go 1.22 changed the behavior of ServeMux to accept extended
patterns and unescape both patterns and request paths by segment.
This behavior can be controlled by the
[`httpmuxgo121` setting](/pkg/net/http/#ServeMux).

Go 1.22 added the [Alias type](/pkg/go/types#Alias) to [go/types](/pkg/go/types)
for the explicit representation of [type aliases](/ref/spec#Type_declarations).

  and some less so—treatment of escaped paths has been improved.
  The change is controlled by a <a href="/doc/godebug"><code>GODEBUG</code></a> field named <code>httpmuxgo121</code>.
  Set <code>httpmuxgo121=1</code> to restore the old behavior.
</p>

<h3 id="minor_library_changes">Minor changes to the library</h3>

<p>
  As always, there are various minor changes and updates to the library,