Interface Go with C libraries

How does one interface a Go program with a C library?

I've been browsing Go's source code but I still didn't figured it out. If someone has already done so, could you share, please?

UPDATED: Thanks to @fserb, I am posting some documentation from the Go sources:

> Cgo enables the creation of Go
> packages that call C code.
>
> Usage: cgo [compiler options] file.go
>
> The compiler options are passed
> through uninterpreted when invoking
> gcc to compile the C parts of the
> package.
>
> The input file.go is a syntactically
> valid Go source file that imports the
> pseudo-package "C" and then refers to
> types such as C.size_t, variables such
> as C.stdout, or functions such as
> C.putchar.
>
> If the import of "C" is immediately
> preceded by a comment, that comment is
> used as a header when compiling the C
> parts of the package. For example:
>
> <!-- -->
>
// #include <stdio.h>
// #include <errno.h>
import "C"
>
> Cgo transforms the input file into
> four output files: two Go source
> files, a C file for 6c (or 8c or 5c),
> and a C file for gcc.
>
> The standard package makefile rules in
> Make.pkg automate the process of using
> cgo. See $GOROOT/misc/cgo/stdio and
> $GOROOT/misc/cgo/gmp for examples.
>
> Cgo does not yet work with gccgo.

Check cgo. Also, take a look at misc/cgo/gmp on the Go source code for an example code on how to wrap a C library in Go.