My devise User model custom field username always nil. I have tried all the other solutions on stack overflow

My application controller file

  class ApplicationController < ActionController::Base
  # Prevent CSRF attacks by raising an exception.
  # For APIs, you may want to use :null_session instead.
  protect_from_forgery with: :exception
  before_action :configure_permitted_parameters, if: :devise_controller?

  protected
  def configure_permitted_parameters
    devise_parameter_sanitizer.permit(:sign_up)  {|u| u.permit(:username, :email, :password, :password_confirmation, :remember_me)}
    devise_parameter_sanitizer.permit(:sign_in)  {|u| u.permit(:username, :email, :password, :password_confirmation, :remember_me)}
    devise_parameter_sanitizer.permit(:account_update) {|u| u.permit(:email, :password, :password_confirmation, :remember_me)}
  end
end

My routes.rb file

Rails.application.routes.draw do
  devise_for :users

  root 'pages#index'

  get 'home' => 'pages#home'

  get 'profile' => 'pages#profile'

  get 'explore' => 'pages#explore'


end

My migration files

class DeviseCreateUsers < ActiveRecord::Migration
  def change
    create_table :users do |t|
      ## Database authenticatable
      t.string :email,              null: false, default: ""
      t.string :encrypted_password, null: false, default: ""

      ## Recoverable
      t.string   :reset_password_token
      t.datetime :reset_password_sent_at

      ## Rememberable
      t.datetime :remember_created_at

      ## Trackable
      t.integer  :sign_in_count, default: 0, null: false
      t.datetime :current_sign_in_at
      t.datetime :last_sign_in_at
      t.string   :current_sign_in_ip
      t.string   :last_sign_in_ip

      ## Confirmable
      # t.string   :confirmation_token
      # t.datetime :confirmed_at
      # t.datetime :confirmation_sent_at
      # t.string   :unconfirmed_email # Only if using reconfirmable

      ## Lockable
      # t.integer  :failed_attempts, default: 0, null: false # Only if lock strategy is :failed_attempts
      # t.string   :unlock_token # Only if unlock strategy is :email or :both
      # t.datetime :locked_at


      t.timestamps null: false
    end

    add_index :users, :email,                unique: true
    add_index :users, :reset_password_token, unique: true
    # add_index :users, :confirmation_token,   unique: true
    # add_index :users, :unlock_token,         unique: true
  end
end

My add username column migration

class AddUsernameToUsers < ActiveRecord::Migration
  def change
    add_column :users, :username, :string
    add_index :users, :username, unique: true
  end
end

My views/devise/registrations/new.html.erb

<%= bootstrap_devise_error_messages! %>
<div class="panel panel-default devise-bs">
  <div class="panel-heading">
    <h4><%= t('.sign_up', default: 'Sign up') %></h4>
  </div>
  <div class="panel-body">
    <%= form_for(resource, as: resource_name, url: registration_path(resource_name), html: { role: 'form' }) do |f| %>
      <div class="form-group">
        <%= f.label :username %>
        <%= f.text_field :email, autofocus: true, class: 'form-control' %>
      </div>
      <div class="form-group">
        <%= f.label :email %>
        <%= f.email_field :email, class: 'form-control' %>
      </div>
      <div class="form-group">
        <%= f.label :password %>
        <%= f.password_field :password, class: 'form-control' %>
      </div>
      <div class="form-group">
        <%= f.label :password_confirmation %>
        <%= f.password_field :password_confirmation, class: 'form-control' %>
      </div>
      <%= f.submit t('.sign_up', default: 'Sign up'), class: 'btn btn-primary' %>
    <% end %>
  </div>
</div>
<%= render 'devise/shared/links' %>

So even after using strong parameters when the usernames being added through browser are not reflected back in the database.

It gives this result

irb(main):001:0> u = User.all
  User Load (20.0ms)  SELECT "users".* FROM "users"
=> #<ActiveRecord::Relation [#<User id: 1, email: "[email protected]", created_at: "2017-07-05 19:42:19", updated_at: "2017-07-05 21:11:38", username: nil>, #<User id: 2, email: "[email protected]", created_at: "2017-07-06 08:45:18", updated_at: "2017-07-06 08:45:18", username: nil>, #<User id: 3, email: "[email protected]", created_at: "2017-07-06 08:56:15", updated_at: "2017-07-06 08:56:15", username: nil>, #<User id: 4, email: "[email protected]", created_at: "2017-07-06 09:23:55", updated_at: "2017-07-06 09:23:55", username: nil>]>

Any help will be appreciated. Also tell me if you need to see any other files.