sql: Select into []*T returns nil pointers, and a struct with an unexported field matching a column panics #4426

Summary

DB.Select (ctx.SQL.Select) has two problems with struct destinations:

1. A []*T destination comes back with N nil pointers. The rows are counted but never scanned into the elements, and no error is reported.
2. A struct with an unexported field that matches a column panics: reflect.Value.Interface: cannot return value obtained from unexported field or method.

Reproduction

In-process sqlite, table users(id, name) with rows (1,'a') and (2,'b'):

type User struct {
	ID   int
	Name string
}

var us []*User
db.Select(ctx, &us, "SELECT id, name FROM users")
// us[0] = <nil>, us[1] = <nil>

type Row struct {
	id   int // unexported
	Name string
}

var rs []Row
db.Select(ctx, &rs, "SELECT id, name FROM users")
// panic: reflect.Value.Interface: cannot return value obtained from unexported field or method
//   sql.(*DB).rowsToStruct db.go:345

Root cause

pkg/gofr/datasource/sql/db.go:

• Pointer elements: selectSlice (line 266) only maps rows into structs when the element kind is Struct. For *T it falls through to rows.Scan with a **T. That fails, and the error is discarded, so a nil element is appended per row.
• Unexported fields: rowsToStruct builds scan targets with v.Field(i).Addr().Interface() (line 345) for every field whose name matches a column. It never checks IsExported(), so the call panics on an unexported field.

Impact

• []*Model is a very common Go idiom. With it, handlers silently get nil entries (and nil-pointer panics later) instead of data.
• Models with private helper fields that happen to share a column name panic the request.

Suggested fix

• In selectSlice, handle Elem().Kind() == Ptr && Elem().Elem().Kind() == Struct: allocate with reflect.New(elem.Elem()), fill it via rowsToStruct and append the pointer.
• Skip fields that are unexported or tagged db:"-" in rowsToStruct, as encoding/json and sqlx do.
• Log (or return) scan errors rather than dropping them.