Gulp process doesn't exit when executed from npm script about gulp HOT 6 CLOSED

var gulp = require('gulp');
var less = require('gulp-less');
var path = require('path');

gulp.task('css', function(){
  gulp.src('./static/src/*.less')
    .pipe(less({
      compress: true,
      paths: [
        path.join(__dirname, 'static/src/less'),
        path.join(__dirname, 'static/src/bootstrap')
      ]
    }))
    .pipe(gulp.dest('./static/dist/css'));
});

gulp.task('default', function(){
  gulp.run('css');
});

{
  "dependencies":{
    "gulp":"*",
    "gulp-less":"*"
  },
  "scripts":{
    "build":"gulp"
  }
}