my gulpfile

gulpfile.js

const gulp = require('gulp');
const pug = require('gulp-pug');
const sass = require('gulp-sass');
const browsersync = require('browser-sync').create();



// Build HTML
function html() {
  return gulp.
  	src("./pug/*.pug")
    .pipe(pug({ pretty: true }))
    .pipe(gulp.dest("./src/"))
    .pipe(browsersync.stream());
}

// BrowserSync server
function browserSync(done) {
    browsersync.init({
        server: {
            baseDir: "./src/"
        }
    });
    done();
}

// BrowserSync Reload
function browserSyncReload(done) {
  browsersync.reload();
  done();
}

// CSS task
function css() {
  return gulp
    .src("./sass/*.sass")
	.pipe(sass({ outputStyle: "expanded" }))
    .pipe(gulp.dest("./src/css/"))
    .pipe(browsersync.stream());
}

// Watch Files
function watchFiles() {
	 gulp.watch("./sass/**/*", css);
	 gulp.watch("./pug/**/*", html);
   gulp.watch(
    [
      "./src/*.html",
      "./src/css/*.css",
    ],
    browserSyncReload);
}

// define complex task
const watch = gulp.parallel(html, watchFiles, browserSync);

// export tasks
exports.html = html;
exports.watch = watch;
exports.css = css;
exports.default = watch;