Update go-sql-driver/mysql to 1.7.1

[php-coder]

Changelogs:

• https://github.com/go-sql-driver/mysql/releases/tag/v1.5.0
• https://github.com/go-sql-driver/mysql/releases/tag/v1.6.0
• https://github.com/go-sql-driver/mysql/releases/tag/v1.7.0
• https://github.com/go-sql-driver/mysql/releases/tag/v1.7.1