Load modules per-task from within the task itself for performance https://github.com/gruntjs/grunt/issues/975

task-server.js

module.exports = function(grunt) {

    grunt.registerTask('server', function (target) {
        
        if (target === 'build') {
            
            return grunt.task.run([
                'build',
                'open',
                'connect:build:keepalive'
            ]);

        }
        // Loading tasks as needed
        grunt.loadNpmTasks('grunt-contrib-clean');
        grunt.loadNpmTasks('grunt-concurrent');
        grunt.loadNpmTasks('grunt-grunticon');
        grunt.loadNpmTasks('grunt-contrib-copy');
        grunt.loadNpmTasks('grunt-contrib-connect');
        grunt.loadNpmTasks('grunt-open');
        grunt.loadNpmTasks('grunt-contrib-watch');
        grunt.loadNpmTasks('grunt-contrib-compass');
        grunt.loadNpmTasks('assemble');

        grunt.task.run([
            'clean:server',
            'concurrent:server',
            'grunticon',
            'copy:server',
            'connect:livereload',
            'open',
            'watch'
        ]);
    });

}