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Notes sur Go

Expertise (3/5)

Je me suis formé au langage GO pour me faire une idée précise de ce qu’il est possible de faire avec.

J’apprécie beaucoup ce langage. À l’heure où j’écris ces lignes (novembre 2012), il me semble que GO est vraiment adapté au développement d’applications système et réseau.

Ci-dessous, je fournis quelques scripts qui simplifient l’utilisation de l’environnement de compilation.

Vous trouverez également le lien vers un client STUN que j’ai développé dans le but de me former (GoStun).

Installation
Utilisation
- L'arborescence de répertoire du projet
- Les variables d'environnement
Un client STUN en GO

Installation

L’installation de l’environnement de développent est plus ou moins automatisée, en fonction du système d’exploitation ciblé, et du mode d'installation.

Quel que soit le système d’exploitation ciblé, la première chose à faire est de s’assurer que le chemin vers les outils de développements fait partie de la variable d’environnement PATH. Ces outils sont:

go
godoc
gofmt

Utilisation

Afin d’utiliser les outils de développement, il faut au préalable :

Créer une arborescence de répertoire avec une structure bien précise. Cette arborescence est destinée à contenir les codes sources ainsi que les binaires générés.
Configurer certaines variables d’environnement.

L'arborescence de répertoire du projet

Racine
├───bin
├───pkg
└───src

Les fichiers qui composent le projet sont classés dans trois sous-répertoires :

bin: les binaires générés.
pkg: les packages locaux au projet.
src: les sources du projets (les fichiers ".go").

Les variables d'environnement

Les scripts ci-dessous permettent de configurer automatiquement l’environnement de compilation pour un projet donné. Ces scripts doivent être placés dans le répertoire racine du projet.

Une version du script est destinée à être utilisée sous Windows (via MSDOS). L’autre version est destinée à être utilisée sous un environnement UNIX (via Bash).

Windows (MSDOS)

@ECHO OFF

REM This script sets the environment variable for a given "GO" project.
REM
REM Usage:
REM   Copy this script at the top level directory of the project.
REM   Open the MSDOS window you will use to compile the project.
REM   Then run this script.
REM 
REM Copyright (C) 2012 Denis BEURIVE
REM 
REM This program is free software: you can redistribute it and/or modify
REM it under the terms of the GNU General Public License as published by
REM the Free Software Foundation, either version 3 of the License, or
REM (at your option) any later version.
REM 
REM This program is distributed in the hope that it will be useful,
REM but WITHOUT ANY WARRANTY; without even the implied warranty of
REM MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
REM GNU General Public License for more details.
REM 
REM You should have received a copy of the GNU General Public License
REM along with this program. If not, see <http://www.gnu.org/licenses/>

REM Make sure that the command GO.EXE is in the PATH.
SET Found=FALSE
FOR %%i IN (%PATH%) DO IF EXIST %%i.\GO.EXE SET Found=TRUE
IF "%Found%" == "TRUE" GOTO goexefound 
  ECHO ERROR: Command GO.EXE was *NOT* found in PATH.
  ECHO Please set the PATH environment variable so that it contains the directory the "GO.EXE" command.
  goto error
:goexefound


REM What is the directory the present batch file being executed in?
SET PWD=%~dp0

REM Make sure that the environment variable GOPATH points to the project's top level directory.
echo Make sure that the environment variable GOPATH points to the project's top level directory.
echo Setting GOPATH to %PWD%.
SET GOPATH=%PWD%

REM Check that the environment variable GOOS is *NOT* set.
IF "%GOOS%" == "" GOTO :endif
   ECHO WARNING: Environment variable GOOS is set (%GOOS%)! Unset it.
   SET GOOS=
:endif

REM Check that the environment variable GOARCH is *NOT* set.
IF "%GOARCH%" == "" GOTO :endif
   ECHO WARNING: Environment variable GOARCH is set (%GOARCH%)! Unset it.
   SET GOARCH=
:endif

REM Check that the environment variable GOROOT is set.
IF NOT "%GOROOT%" == "" GOTO :endif
   ECHO ERROR: Environment variable GOROOT is not set!.
   ECHO Please set this environment variable to the top level directory of the GO installation.
   goto error
:endif

REM By default, the command "go install <package name>" will install programs into the directory "GOPATH/bin".
REM That's what we want. Therefore, check that the environment variable GOBIN is not set.
IF "%GOBIN%" == "" GOTO :endif
   ECHO WARNING: Environment variable GOBIN is set (%GOBIN%))! Unset it.
   SET GOBIN=
:endif

ECHO.
ECHO OK
GOTO final

:error
ECHO.
ECHO An error occurred while checking environment variables.
EXIT /B 1

:final

UNIX (Bash)

#!/bin/bash
#
# This script sets the environment variable for a given "GO" project.
#
# Usage:
#   Copy this script at the top level directory of the project.
#   Then "source" this script. Ie: . env.bash
#
# Copyright (C) 2012 Denis BEURIVE
# 
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>


OS=$(uname)
echo "OS: $OS"


# Make sure that the path to the GO command is in the PATH.
GO=$(which go)
if [ ! -n "$GO" ]; then
  echo "ERROR: Command \"go\" was *NOT* found in PATH."
  echo "Please set the PATH environment variable so that it contains the directory of of command \"go\"."
  return 1
fi

# What is the directory the present batch file being executed in?
SOURCE="${BASH_SOURCE[0]}"
while [ -h "$SOURCE" ] ; do SOURCE="$(readlink "$SOURCE")"; done
PWD="$( cd -P "$( dirname "$SOURCE" )" && pwd )"

# Make sure that the environment variable GOPATH points to the project's top level directory.
echo "Setting GOPATH to $PWD"
GOPATH=$PWD
export GOPATH

# Check that the environment variable GOOS is *NOT* set.
if [ -n "$GOOS" ]; then
  echo "WARNING: Environment variable GOOS is set!"
  echo "Unset it."
  unset GOOS
fi

# Check that the environment variable GOARCH is *NOT* set.
if [ -n "$GOARCH" ]; then
  echo "WARNING: Environment variable GOARCH is set!"
  echo "Unset it."
  unset GOARCH
fi

# Check that the environment variable GOROOT is set.
if [ ! -n "$GOROOT" ]; then
  echo "WARNING: Environment variable GOROOT is not set! Try to set it..."
  GO=$(which go)
  if [ -n "$GO" ]; then
    D=$(dirname "$GO")
    GOROOT=$(dirname "$D")
    export GOROOT
    echo "Set GOROOT to $GOROOT"
    if [ "$OS" == 'Darwin' ]; then
      launchctl setenv GOROOT $GOROOT
    fi
  else
    echo "ERROR: Can not set GOROOT!"
    return 1
  fi
fi

# By default, the command "go install <package name>" will install programs into the directory "GOPATH/bin".
# That's what we want. Therefore, check that the environment variable GOBIN is not set.
# Check that the environment variable GOARCH is *NOT* set.
if [ -n "$GOBIN" ]; then
  echo "WARNING: Environment variable GOBIN is set!"
  echo "Unset it."
  Unset GOBIN
fi

Un client STUN en GO

J’ai développé ce client STUN pour me former sur le langage GO. STUN est un protocole qui permet à un client placé sur un réseau privé de déterminer s’il est derrière un NAT. Le cas échéant, STUN permet de déterminer le type de NAT.

https://github.com/denis-beurive/GoStun