func write_tx_file(tx *btc.Tx) {
signedrawtx := tx.Serialize()
tx.SetHash(signedrawtx)
hs := tx.Hash.String()
fmt.Println(hs)
f, _ := os.Create(hs[:8] + ".txt")
if f != nil {
f.Write([]byte(hex.EncodeToString(signedrawtx)))
f.Close()
fmt.Println("Transaction data stored in", hs[:8]+".txt")
}
}