Cannot transfer money on standalone network

Question

I'm attempting to transfer funds from the root account to another account on a private stellar network. When I attempt to run the code below (which is basically copied from the examples), I get an error that says the following when I sign the transaction:

hash tx failed: empty network passphrase

The full code is below, where did I go wrong?

package main

import (
    "fmt"
    "github.com/pkg/errors"
    "log"
    "net/http"

    b "github.com/stellar/go/build"
    "github.com/stellar/go/clients/horizon"
    "github.com/stellar/go/keypair"
)

func main() {
    // Root account seed, found in the startup log
    from := "XXXXXXXXXXXXXXXXXXXXXXXXX"

    pair, err := keypair.Random()
    if err != nil {
        log.Fatal(err)
    }

    // Create a new account keypair
    to := pair.Address()

    client := &horizon.Client{
        URL:  "http://127.0.0.1:8000",
        HTTP: http.DefaultClient,
    }

    tx, herr := b.Transaction(
        b.SourceAccount{AddressOrSeed: from},
        b.DefaultNetwork,
        b.AutoSequence{SequenceProvider: client},
        b.Payment(
            b.Destination{AddressOrSeed: to},
            b.NativeAmount{Amount: "100"},
        ),
    )

    if herr != nil {
        //panic(herr.(horizon.Error).Problem.Type)
        panic(errors.WithStack(herr))
    }

    txe, err := tx.Sign(from)
    if err != nil {
        panic(err)
    }

    txe64, err := txe.Base64()
    if err != nil {
        panic(err)
    }

    fmt.Printf("tx base64: %s", txe64)

    resp, err := horizon.DefaultTestNetClient.SubmitTransaction(txe64)
    if err != nil {
        panic(err)
    }

    fmt.Println("transaction posted in ledger:", resp.Ledger)
}

Answer 1

It looks like I hadn't set the passphrase in the code. The tx should look like the following:

tx, herr := b.Transaction(
    b.SourceAccount{AddressOrSeed: from},
    b.Network{"Network Passphrase""},
    b.AutoSequence{SequenceProvider: client},
    b.Payment(
        b.Destination{AddressOrSeed: to},
        b.NativeAmount{Amount: "100"},
    ),
)

Notice the change from b.DefaultNetwork to b.Network{"Network Passphrase"}