我尝试用crystalmysql连接kemal框架。这是我的碎片：

mysql:
github: crystal-lang/crystal-mysql
db:
    github: crystal-lang/crystal-db

这是我的联系：

db = DB.open "mysql://root:password@localhost:787878/book"

但是，如果我在跑步 crystal src/book.cr 我有一个错误：

Unhandled exception:  (DB::ConnectionLost)
  from lib/mysql/src/mysql/read_packet.cr:16:7 in 'initialize'
  from lib/mysql/src/mysql/read_packet.cr:6:3 in 'new'
  from lib/mysql/src/mysql/connection.cr:77:5 in 'build_read_packet'
  from lib/mysql/src/mysql/connection.cr:59:5 in 'read_packet'
  from lib/mysql/src/mysql/connection.cr:22:19 in 'initialize'
  from lib/mysql/src/mysql/connection.cr:4:3 in 'new'
  from lib/mysql/src/mysql/driver.cr:3:5 in 'build_connection'
  from lib/db/src/db/database.cr:51:9 in '->'
  from lib/db/src/db/pool.cr:255:3 in 'build_resource'
  from lib/db/src/db/pool.cr:17:34 in 'initialize'
  from lib/db/src/db/pool.cr:15:5 in 'new:initial_pool_size:max_pool_size:max_idle_pool_size:checkout_timeout:retry_attempts:retry_delay'
  from lib/db/src/db/database.cr:50:7 in 'initialize'
  from lib/db/src/db/database.cr:43:5 in 'new'
  from lib/db/src/db.cr:139:5 in 'build_database'
  from lib/db/src/db.cr:135:5 in 'build_database'
  from lib/db/src/db.cr:103:5 in 'open'
  from src/news_monitoring.cr:13:1 in '__crystal_main'
  from /usr/share/crystal/src/crystal/main.cr:97:5 in 'main_user_code'
  from /usr/share/crystal/src/crystal/main.cr:86:7 in 'main'
  from /usr/share/crystal/src/crystal/main.cr:106:3 in 'main'
  from __libc_start_main
  from _start
  from ???

我怎么能修好它。