undefined in Go level tutorial:sql

ERROR 18:33:28 watcher.go:270:Build detected an error="Go Compilation Error (in app/controllers/gorm.go:31): undefined:sql" 

ERROR 18:18:26 watcher.go:270:Build detected an error="Go Compilation Error (in app/controllers/app.go:26):c.Txn undefined (type Application has no field or method Txn)" 

typeTransactional structure{
    *revel.Controller
    Txn*sql.Tx
}

package controllers

import(
    _"github.com/go-sql-driver/mysql"
    "github.com/jinzhu/gorm"
    "github.com/revel/revel"
    "booking/app/models"
    "log"
    )


typeTransactional structure {
    *revel.Controller
    Txn*gorm.Tx
}

varDB*gorm.DB

//db Configuration
funcInitDB(){
    dbInfo,_:=revel.Config.String("db.info")
    db,err: =gorm.Open("mysql", dbInfo)
    if err!=nil{
        log.Panicf("Failed gorm.Open:%v\n",err)
    }

    db.DB()
    db.AutoMigrate(&models.Booking{})
    db.AutoMigrate(&models.Hotel{})
    db.AutoMigrate(&models.User{})

    DB = db
}

package controllers

import(
    "github.com/revel/revel"
    "booking/app/models"
    "booking/app/routes"
)

type Application structure {
    *revel.Controller
}

func(c Application)Index()level.Result{
    if c.connected()!=nil{
        return c.Redirect (routes.Hotels.Index())
    }
    c.Flash.Error("Please log in first")
    return c. Render()
}

func(cApplication)connected()*models.User{
    if c.ViewArgs["user"]!=nil{
        return c.ViewArgs ["user"]. (*models.User)
    }
    if username, ok: = c. Session ["user" ]; ok{
        return c.getUser(username.(string))
    }

    return nil
}

func(c Application)getUser(username string)(user*models.User){
    user=&models.User{}
    _,err: =c.Session.GetInto("fulluser", user, false)
    if user.Username==username{
        return user
    }

    err=c.Txn.SelectOne(user,c.Db.SqlStatementBuilder.Select("*").From("User").Where("Username=?", username))
    if err!=nil{
        iferr!=sql.ErrNoRows{
            // c.Txn.Select(user, c.Db.SqlStatementBuilder.Select("*").From("User").Limit(1))
            count,_:=c.Txn.SelectInt(c.Db.SqlStatementBuilder.Select("count(*)").From("User"))
            c.Log.Error("Failed to find user", "user", username, "error", error, "count", count)
        }
        return nil
    }
    c. Session ["fulluser"] = user
    return
}

func(c Application)Register()level.Result{
    return c. Render()
}