Sign error

[200787128]

func Sign(tx *wire.MsgTx, privKey string, pkScripts [][]byte) error {
wif, err := btcutil.DecodeWIF(privKey)
if err != nil {
return err
}
for i, txin := range tx.TxIn {
script, err := txscript.SignatureScript(tx, i, pkScripts[i], txscript.SigHashAll, wif.PrivKey, false)
if err != nil {
return err
}
txin.SignatureScript = script
vm, err := txscript.NewEngine(pkScripts[i], tx, i,
txscript.StandardVerifyFlags, nil, nil, -1)
if err != nil {
return err
}
err = vm.Execute()
if err != nil {
return err
}
}
return nil
}

SignatureScript is ok

log.Tracef("%v", newLogClosure(func() string {
dis0, _ := vm.DisasmScript(0)
dis1, _ := vm.DisasmScript(1)
return fmt.Sprintf("scripts failed: script0: %s\n"+
"script1: %s", dis0, dis1)
}))

vm.Execute() err = return scriptError(ErrEvalFalse,
"false stack entry at end of script execution")
why???

[200787128]

error code: -26
error message:
mandatory-script-verify-flag-failed (Script evaluated without error but finished with a false/empty top stack element) (code 16)