go语言操作mysql数据库问题

hi 我用github.com/Go-SQL-Driver/Mysql操作mysql 例子参照go web 编程教程 增改删按顺序操作没问题，但是只修改就报错，求助大神是什么原因造成的？ 报错信息： .\test.go:47: undefined: stmt .\test.go:48: undefined: res .\test.go:48: undefined: stmt .\test.go:49: undefined: res //代码如下： package main import ( "database/sql" "fmt" _ "github.com/Go-SQL-Driver/Mysql" ) func main() { db, err := sql.Open("mysql", "root:@/test?charset=utf8") //checkErr(err, "连接成功") // stmt, err := db.Prepare("INSERT into userinfo (username, departname, created) values (?,?,?)") // res, err := stmt.Exec("astaxie", "研发部门", "2012-12-09") // checkErr(err, "插入成功") // fmt.Println(res) stmt, err = db.Prepare("UPDATE userinfo set username=? where uid=?") res, err = stmt.Exec("astaxieupdate", 12) affect, err := res.RowsAffected() checkErr(err, "更新成功") fmt.Println(affect) // //查询数据 // rows, err := db.Query("SELECT * FROM userinfo") // for rows.Next() { // var uid int // var username string // var department string // var created string // err = rows.Scan(&uid, &username, &department, &created) // checkErr(err, "查询") // fmt.Println(uid) // fmt.Println(username) // fmt.Println(department) // fmt.Println(created) // } //删除数据 // stmt, err = db.Prepare("delete from userinfo where uid=?") // res, err = stmt.Exec(30) // fmt.Println(res) // db.Close() } func checkErr(err error, msg string) { if err != nil { panic(err) } else { fmt.Println(msg) } }