[sqlx] does not support struct fields with lowercase (unexported) names.

[jiangf0775]

Describe the bug
sqlx不支持结构体小写的变量名

To Reproduce
Steps to reproduce the behavior, if applicable:

1. The code is

func main() {
DbQuery()
}

func NewMysql() sqlx.SqlConn {
mysql := sqlx.NewMysql("xxx")
db, err := mysql.RawDB()
if err != nil {
panic(err)
}

ctx, cancel := context.WithTimeout(context.Background(), time.Second*60)
defer cancel()

err = db.PingContext(ctx)
if err != nil {
	panic(err)
}
return mysql

}
func DbQuery() {
mysql := NewMysql()
var resp []BaseOption
ctx, cancel := context.WithTimeout(context.Background(), time.Second60)
defer cancel()

query := "select * from base_option where deleted = ?"
var values = []interface{}{0}

err := mysql.QueryRowsCtx(ctx, &resp, query, values...)
if err != nil {
	fmt.Println(err)
	return
}
for _, v := range resp {
	// fmt.Println(v)
	fmt.Printf("%+v \n", v)
}

}
type (
BaseModel struct {
Id uint64 db:"id"
Deleted uint64 db:"deleted"
CreatedDate time.Time db:"created_date"
CreatedUserName string db:"created_user_name"
CreatedUserId uint64 db:"created_user_id"
ModifiedDate sql.NullTime db:"modified_date"
ModifiedUserName sql.NullString db:"modified_user_name"
ModifiedUserId sql.NullInt64 db:"modified_user_id"
}
BaseOption struct {
//数据库表映射的结构体
Name string db:"name"
Value string db:"value"
description sql.NullString db:"description"//****小写变量名
BaseModel db:"-"
}
)

func (m *BaseOption) GetDesc() string {
return m.description.String
}
func (m *BaseOption) SetDesc() {

}

2. The error is

value not addressable or interfaceable

**Expected behavior**
A clear and concise description of what you expected to happen.

**Screenshots**
If applicable, add screenshots to help explain your problem.

**Environments (please complete the following information):**
- OS: [e.g. Windows]
- go-zero version [e.g. v1.7.4]
- goctl version [e.g. 1.21.6]

**More description**

[hthuz]

Underlying QueryRowsCtx, reflect.Value.Interface() is used to parse the fields of struct. But unexported fields can't be accessed with reflect, possible for safety reason. Actually, if you json.Marshal/Unmarshal a struct, unexported fields won't be marshaled/unmarshaled.
So I believe the simplest solution is to use uppercase names. Or use an intermediate struct with all uppercase names for query if you need lowercase names.