以下任务未完成:发球、sass。您忘记发出异步完成的信号了吗?

其他答案没有帮助。我正在Windows 10上使用Gulp 4。

运行“gulp serve”时出现以下错误

The following tasks did not complete: serve, sass
[18:48:51] Did you forget to signal async completion?

我的gulpfile。js公司

var gulp = require('gulp');
var sass = require('gulp-sass');
var browserSync = require('browser-sync');
var reload = browserSync.reload;

gulp.task('sass', function() {
    return sass('./public_html/lib/scss/main.scss')
        .pipe(gulp.dest('./public_html/css'))
        .pipe(reload({ stream:true }));
});
gulp.task('serve', gulp.series('sass', function() {
    browserSync({
        server: {
            baseDir: 'public_html'
        }
    });
    gulp.watch('lib/scss/*.scss', gulp.series('sass'));
}));