Gulp Concat does not work

Question

Good morning. I am unable to concatenate the Angularjs files using the Gulp Concat module. I tried to change the directory file and it still doesn’t work. The problem is that I don’t see any error, just don’t concatenate. All tasks run well, only the one that is giving problem.

var gulp = require('gulp');

    var clean = require('gulp-clean');
    var jshint = require('gulp-jshint');
    var concat = require('gulp-concat');
    var uglify = require('gulp-uglify');
    var imagemin = require('gulp-imagemin');

    var bases = {
        app: 'app/',
        dist: 'dist/',
    };

    var paths = {
        scripts: ['scripts/**/*.js', '!scripts/libs/**/*.js'],
        libs: ['scripts/libs/angular/angular.min.js', 'scripts/libs/angular/angular-animate.js', 'scripts/libs/angular/angular-messages.min.js','scripts/libs/angular/angular-resource.min.js'],
        styles: ['styles/**/*.css'],
        html: ['index.html'],
        images: ['images/**/*.png']
    };

    gulp.task('clean', function() {
        return gulp.src(bases.dist)
        .pipe(clean());
    });

    gulp.task('scripts', ['clean'], function() {
        gulp.src(paths.scripts, {cwd: bases.app})
        .pipe(jshint())
        .pipe(jshint.reporter('default'))
        .pipe(uglify())
        .pipe(concat('app.min.js'))
        .pipe(gulp.dest(bases.dist + 'scripts/'));
    });

    gulp.task('imagemin', ['clean'], function() {
        gulp.src(paths.images, {cwd: bases.app})
        .pipe(imagemin())
        .pipe(gulp.dest(bases.dist + 'images/'));
    });

    gulp.task('copy', ['clean'], function() {

     gulp.src(paths.html, {cwd: bases.app})
     .pipe(gulp.dest(bases.dist));

     gulp.src(paths.styles, {cwd: bases.app})
     .pipe(gulp.dest(bases.dist + 'styles'));

     gulp.src(paths.libs, {cwd: 'app/**'})
     .pipe(gulp.dest(bases.dist));

    });

    gulp.task('watch', function() {
        gulp.watch('app/**/*', ['scripts', 'copy']);
    });

    gulp.task('default', ['clean', 'scripts', 'imagemin', 'copy']);

Can someone give me a hand?