Code minification of angular app using grunt concat and uglify

Question

I'm using grunt concat and uglify to minify angular app however the minified script is giving the following error.

Uncaught Error: [$injector:modulerr] http://errors.angularjs.org/1.5.9/$injector/modulerr?p0=myapp&p1=Error%…2F%2F192.168.1.244%3A8080%2Fapp%2Fdist%2Fjs%2Fmyapp.min.js%3A5%3A10649)(…)

This is how I have implemented DI in the angular application.

(function() {
    myapp
    
    .controller('MyController',MyController);

    MyController.$inject = ['$scope','$rootScope'];
 
    function MyController($scope,$rootScope) {
      
    }
})();

This is how my gruntfile looks.

module.exports = function(grunt) {
 grunt.initConfig({
  pkg: grunt.file.readJSON('package.json'),
  concat: {
   dist: {
    src: ['node_modules/jquery/dist/jquery.min.js','node_modules/bootstrap/dist/js/bootstrap.min.js','node_modules/angular/angular.min.js'],
    dest: 'dist/js/myapp.js',
   }
  },
   uglify: {
   options: {
    report: 'min',
    mangle: false
   },
   my_target: {
    files: {
     'dist/js/myapp.min.js':['dist/js/myapp.js']
    }
   }
  }
 });
 
 grunt.loadNpmTasks('grunt-contrib-concat');
 grunt.loadNpmTasks('grunt-contrib-uglify');
};

I'm following the proper DI method for angular and why's the error still occuring?