sql中的 #{key}获取不到

[catman002]

package mapper
var XmlBytes = []byte(`
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://raw.githubusercontent.com/zhuxiujia/GoMybatis/master/mybatis-3-mapper.dtd">
<mapper>
    <select id="SelectCountByKey">
        select count(*) as num from ek8keys where ek8key=#{key}
    </select>
</mapper>
`)
type IdentityMapperr struct {
	SelectCountByKey  func(key string) (int, error)
}

调用：
	engine:= config.MysqlServer.Connection()
	engine.WriteMapperPtr(&identityMapper,mapper.XmlBytes)
	result,err1:=identityMapper.SelectCountByKey(key) //key=123456

调用 SelectCountByKey（“123456”）查询，sql中的#{key}获取不到，查出的结果为0，哪配错了啊