Creating Trust line in Go

Question

I am struggling to set a Trustline.

1. Create account
2. Send Funds to New account
3. Set Trust for a Token
4. Send the Token. I am having a big problem trying to get step 3 working, many online examples are using the old method and converting them has its own issues. I created a Function as follows:

func TrustToken(issuedAsset txnbuild.Asset, limit string, targetAccount keypair.Full, sourceAccount keypair.Full) {
    client, _ := connectStellar()

    allowTrust := txnbuild.SetTrustLineFlags{
        Trustor:  targetAccount.Address(),
        Asset:    issuedAsset,
        SetFlags: []txnbuild.TrustLineFlag{txnbuild.TrustLineAuthorized},
    }

    kp, _ := keypair.Parse(sourceAccount.Seed())
    ar := horizonclient.AccountRequest{AccountID: kp.Address()}
    account, err := client.AccountDetail(ar)
    if lib.CheckErr(err) {
        panic(err)
    }

    tx, err := txnbuild.NewTransaction(
        txnbuild.TransactionParams{
            SourceAccount:        &account,
            IncrementSequenceNum: true,
            Operations:           []txnbuild.Operation{&allowTrust},
            Preconditions:        txnbuild.Preconditions{TimeBounds: txnbuild.NewInfiniteTimeout()},
            BaseFee:              txnbuild.MinBaseFee,
        },
    )
    if lib.CheckErr(err) {panic(err)}

    // Sign it.
    txeBase64 := ""
    if mainNetwork() {
        signedTX, _ := tx.Sign(network.PublicNetworkPassphrase, &targetAccount)
        txeBase64, _ = signedTX.Base64()
    } else {
        signedTX, _ := tx.Sign(network.TestNetworkPassphrase, &targetAccount)
        txeBase64, _ = signedTX.Base64()
    }

    resp, errSubmit := client.SubmitTransactionXDR(txeBase64)
    if lib.CheckErr(errSubmit) {
        hError := errSubmit.(*horizonclient.Error)
        lib.Error("Error submitting transaction:", hError.Problem)
    }

}

I removed a few debug statements and noise to simplify this function. but I am getting the error:horizon error: "Transaction Failed" (tx_bad_auth) I really would like to fin a working example somewhere, Google has evaded my searches. and any guidance of finger point will be very apprecated.