panic from driver with a deferred txn rollback = bad time

panic.go

package main

import (
        _ "github.com/lib/pq"
        "database/sql"
        "time"
)

func reproduce(txn *sql.Tx) {
        defer txn.Rollback()

        var v int
        err := txn.QueryRow("SELECT 1").Scan(&v)
        if err != nil {
                panic(err)
        }
}

func main() {
        db, err := sql.Open("postgres", "sslmode=disable")
        if err != nil {
                panic(err)
        }
        txn, err := db.Begin()
        if err != nil {
                panic(err)
        }
        go func() {
                time.Sleep(5 * time.Second)
                panic("stacktrace")
        }()
        reproduce(txn)
        panic("not reached")
}

stacktrace

panic: stacktrace

goroutine 4 [running]:
main.func·001()
        /home/marko/work/panic.go:30 +0x58
created by main.main
        /home/marko/work/panic.go:31 +0xba

goroutine 1 [semacquire]:
sync.runtime_Semacquire(0x18360158)
        /usr/local/go/src/pkg/runtime/zsema_linux_386.c:165 +0x32
sync.(*Mutex).Lock(0x18360154)
        /usr/local/go/src/pkg/sync/mutex.go:66 +0xb6
database/sql.(*Tx).Rollback(0x1835c8a0, 0x0, 0x0)
        /usr/local/go/src/pkg/database/sql/sql.go:877 +0x81
github.com/lib/pq.errRecover(0xb70d4e9c)
        /home/marko/gopath/src/github.com/lib/pq/error.go:465 +0x358
github.com/lib/pq.(*conn).Query(0x18371000, 0x81a7fc8, 0x8, 0x8299c4c, 0x0, ...)
        /home/marko/gopath/src/github.com/lib/pq/conn.go:455 +0x90
database/sql.(*DB).queryConn(0x1836c100, 0x18360150, 0x81da898, 0x81a7fc8, 0x8, ...)
        /usr/local/go/src/pkg/database/sql/sql.go:728 +0x13a
database/sql.(*Tx).Query(0x1835c8a0, 0x81a7fc8, 0x8, 0x0, 0x0, ...)
        /usr/local/go/src/pkg/database/sql/sql.go:1005 +0x94
database/sql.(*Tx).QueryRow(0x1835c8a0, 0x81a7fc8, 0x8, 0x0, 0x0, ...)
        /usr/local/go/src/pkg/database/sql/sql.go:1012 +0x51
main.reproduce(0x1835c8a0)
        /home/marko/work/panic.go:13 +0x70
main.main()
        /home/marko/work/panic.go:32 +0xc8

goroutine 2 [syscall]: