Ebuild example for project in Go

I intend to create a Gentoo ebuild for a project written in Go, and I'm wondering whether this has been done before.

As building and installing a Go project from source seems sufficiently different compared to projects in other programming languages, it would be useful for me to compare to an existing ebuild for figuring out best practices.

However, in the current portage tree I can't find any package that would depend on "dev-lang/go". Is there such an ebuild, perhaps in an overlay?

How about go-overlay to look for example ebuilds? They wrote a special ebuild class for building Go apllications and libraries in a few lines. Let me use their dev-util/flint-0.0.4 ebuild as an illustration (all comments are mine):

EAPI=6

GOLANG_PKG_IMPORTPATH="github.com/pengwynn"
GOLANG_PKG_VERSION="c3a5d8d9a2e04296fba560d9a22f763cff68eb75"

# Many Go projects don't pin versions of their dependencies,
# so it may has to be done here. You might not need this step if
# the upstream already uses 'godep' or simular tool.
GOLANG_PKG_DEPENDENCIES=(
	"github.com/codegangsta/cli:142e6cd241"
	"github.com/fatih/color:1b35f289c4"
	"github.com/octokit/go-octokit:4408b5393e"
	"github.com/fhs/go-netrc:4422b68c9c"
	"github.com/jingweno/go-sawyer:1999ae5763"
	"github.com/shiena/ansicolor:264b056680"
	"github.com/jtacoma/uritemplates:0a85813eca"
)

# Since many projects don't require custom build steps,
# this single line may be enough.
inherit golang-single

# Nothing special about these variables.    
DESCRIPTION="Check your project for common sources of contributor friction"
HOMEPAGE="https://${GOLANG_PKG_IMPORTPATH}/${PN}"    
LICENSE="MIT"
KEYWORDS="amd64 x86 arm"

# Prevent simulateneous installing with 'dev-go/flint'.
# Honestly, I was unable to this package on the Internet.
SLOT="0"
DEPEND="!dev-go/${PN}"

Here is a working example of an ebuild which installs a go project:

https://github.com/timboudreau/gentoo/blob/master/net-misc/syncthing/syncthing-0.11.7.ebuild

It is possible. I just made one in my overlay. It was a little bit painful, but it works.

There are a few important things, that have to be done.

1. Create golang eclasses in your repository, if you don't have go-overlay added in your system.
2. GOLANG_PKG_IMPORTPATH variable specifies a GitHub profile, from which will be downloaded source code.
3. GOLANG_PKG_DEPENDENCIES variable specifies GitHub repositories and particular commits of all dependencies.
4. inherit golang-single imports mentioned eclass and at the same time adds dev-lang/go into dependencies.

It looks like there's an existing, working ebuild.

From: https://gist.github.com/matsuu/233858 (and also found at http://git.overlays.gentoo.org/gitweb/?p=proj/glentoo-overlay.git;a=blob_plain;f=dev-lang/golang-platform/golang-platform-9999.ebuild;hb=HEAD)

# Copyright 1999-2009 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2
# $Header: $
 
EAPI="2"
inherit elisp-common eutils mercurial toolchain-funcs
 
DESCRIPTION="The Go Programming Language"
HOMEPAGE="http://golang.org/"
SRC_URI=""
EHG_REPO_URI="https://go.googlecode.com/hg/"
EHG_REVISION="release"
 
LICENSE="BSD"
SLOT="0"
KEYWORDS="~amd64 ~x86"
IUSE="emacs vim-syntax"
 
RESTRICT="test"
 
RDEPEND="sys-devel/gcc"
DEPEND="${RDEPEND}
	emacs? ( virtual/emacs )
	sys-devel/bison
	sys-apps/ed"
 
S="${WORKDIR}/hg"
 
ENVFILE="${WORKDIR}/50${PN}"
 
src_prepare() {
	GOBIN="${WORKDIR}/bin"
	mkdir -p "${GOBIN}" || die
 
	sed -i \
		-e "/^GOBIN=/s:=.*:=${GOBIN}:" \
		-e "/MAKEFLAGS=/s:=.*:=${MAKEOPTS}:" \
		src/make.bash || die
 
	sed -i \
		-e "/^CFLAGS=/s:-O2:${CFLAGS}:" \
		src/Make.conf || die
	
	case ${ARCH} in
	x86)
		GOARCH="386"
		;;
	*)
		GOARCH="${ARCH}"
		;;
	esac
 
	case ${CHOST} in
	*-darwin*)
		GOOS="darwin"
		;;
	*)
		GOOS="linux"
		;;
	esac
#	*-nacl*)
#		GOOS="nacl"
#		;;
 
	cat > "${ENVFILE}" <<EOF
GOROOT="/usr/$(get_libdir)/${PN}"
GOARCH="${GOARCH}"
GOOS="${GOOS}"
EOF
	. "${ENVFILE}"
 
	export GOBIN GOROOT GOARCH GOOS
}
 
src_compile() {
	cd src
	PATH="${GOBIN}:${PATH}" GOROOT="${S}" CC="$(tc-getCC)" ./make.bash || die
	if use emacs ; then
		elisp-compile "${S}"/misc/emacs/*.el || die
	fi
}
 
src_test() {
	cd src
	PATH="${GOBIN}:${PATH}" GOROOT="${S}" CC="$(tc-getCC)" ./run.bash || die
}
 
src_install() {
	dobin "${GOBIN}"/* || die
 
	insinto "${GOROOT}"
	doins -r pkg || die
 
	if use emacs ; then
		elisp-install ${PN} "${S}"/misc/emacs/*.el* || die "elisp-install failed"
	fi
 
	if use vim-syntax ; then
		insinto /usr/share/vim/vimfiles/plugin
		doins "${S}"/misc/vim/go.vim || die
	fi
 
	doenvd "${ENVFILE}" || die
 
	dodoc AUTHORS CONTRIBUTORS README || die
	dohtml -r doc/* || die
}
 
pkg_postinst() {
	elog "please don't forget to source /etc/profile"
}

Sorry, I haven't tested it as I don't have a running Gentoo instance right now. Hope it works.