code: func (p *MySQLPrivilege) connectionVerification(user, host string) *UserRecord {
  	for i := 0; i < len(p.User); i++ {
  		record := &p.User[i]
  		if record.match(user, host) {
  			return record
  		}
  	}
  	return nil
  }
docs: // connectionVerification verifies the connection have access to TiDB server.