For example:

	// #cgo pkg-config: png cairo
	// #include <png.h>
	import "C"

The default pkg-config tool may be changed by setting the PKG_CONFIG environment variable.

For security reasons, only a limited set of flags are allowed, notably -D, -U, -I, and -l.
To allow additional flags, set CGO_CFLAGS_ALLOW to a regular expression
matching the new flags. To disallow flags that would otherwise be allowed,

controlled by the [`panicnil` setting](/pkg/builtin/#panic).

Go 1.21 made it an error for html/template actions to appear inside of an ECMAScript 6
template literal, controlled by the
[`jstmpllitinterp` setting](/pkg/html/template#hdr-Security_Model).
This behavior was backported to Go 1.19.8+ and Go 1.20.3+.

Go 1.21 introduced a limit on the maximum number of MIME headers and multipart
forms, controlled by the