rails deploy migrating run with root

When i do deploy, migrating run as root. i have error: Mysql2::Error: Access denied for user 'root'@'localhost' (using password: YES) But in my /shared/config/database.yml

default: &default
  adapter: mysql2
  pool: 5
  timeout: 5000
  database: sa

development:
  <<: *default
  user: root
  password: ""

test:
  <<: *default
  database: db/test.sqlite3

production:
  <<: *default
  user: sa
  password: "mypassss"

my capfile:

 require "capistrano/rvm"
 require "capistrano/bundler"
 require "capistrano/rails/migrations"
 require "capistrano/passenger"

Why migrating run as root but not as user sa?