Auto reload your Go webserver with Gulp

3 min readMar 17, 2016

When you developp a webserver with Go, you must compile each time you do an update in your code. Well.. this is redundant. With Gulp you can automatize this task… Indeed, when a go file is modified, a task compile the application in the “bin” folder (“gopath/bin”) then another launch the executable (the webserver).

So we have 3 distincts tasks :

Application compile ;
Lauching application / server ;
Watching for files modified.

Before starting, check you have NodeJS & NPM installed on your machine.

node -v && npm -v

And the environnement variable for “GOPATH” with

go env

If “GOPATH” is empty, set the variable environnement. More details : https://golang.org/doc/code.html#GOPATH

Gulpfile

In your application folder, create a “package.json” file.

{
 "devDependencies": {
 "gulp": "^3.8.11",
 "gulp-util": "*",
 "gulp-sync": "*",
 "gulp-livereload": "*",
 "node-notifier": "*"
 }
}

Then install these modules with the command

npm install

Create a “Gulpfile.js” with these dependences.

const gulp     = require('gulp'),
      util     = require('gulp-util'),
      notifier = require('node-notifier'),
      sync     = require('gulp-sync')(gulp).sync,
      reload   = require('gulp-livereload'),
      child    = require('child_process'),
      os       = require('os');var server = null;// Tasks incoming

Application compile

// Compile application
gulp.task('server:build', function() { var build = child.spawnSync('go', ['install']);
 return build;});

Except that it’s not over because compilation errors are not including.

// Compile application
gulp.task('server:build', function() { // Build application in the "gobin" folder
 var build = child.spawnSync('go', ['install']); // Something wrong
 if (build.stderr.length) {
  util.log(util.colors.red('Something wrong with this version :'));
  var lines = build.stderr.toString()
   .split('\n').filter(function(line) {
   return line.length
 });
 for (var l in lines)
  util.log(util.colors.red(
   'Error (go install): ' + lines[l]
  ));
  notifier.notify({
   title: 'Error (go install)',
   message: lines
 });
}return build;});

Errors are now displaying in the terminal and in a notify window.

Launch server

// Launch server
gulp.task('server:spawn', function() { // Stop the server
 if (server && server !== 'null') {
  server.kill();
 } // Application name
 if (os.platform() == 'win32') {
  // Windows
  var path_folder = __dirname.split('\\');
 } else {
  // Linux / MacOS
  var path_folder = __dirname.split('/');
 }
 var length = path_folder.length;
 var app    = path_folder[length - parseInt(1)]; // Run the server
 if (os.platform() == 'win32') {
  server = child.spawn(app + '.exe');
 } else {
  server = child.spawn(app);
 } // Display terminal informations
 server.stderr.on('data', function(data) {
  process.stdout.write(data.toString());
 });});

Watching files

// Watch files
gulp.task('server:watch', function() { gulp.watch([
 '*.go',
 '**/*.go',
 ], sync([
 'server:build',
 'server:spawn'
 ], 'server'));});

This task watching go files presents in the current folder and subfolders of your application.

Let’s play…

At the end of your Gulpfile, at this line for executing our 3 tasks.

gulp.task('default', ['server:build', 'server:spawn', 'server:watch']);

Then run with the default gulp command.

gulp

Complete code available in this Gist.