Factom-Asset-Tokens/fatd: cli/transact.go; 13 LoC

Found a possible issue in [Factom-Asset-Tokens/fatd](https://www.github.com/Factom-Asset-Tokens/fatd) at [cli/transact.go](https://github.com/Factom-Asset-Tokens/fatd/blob/f8331d1d63aad652e6ae481475458bb57a037f5b/cli/transact.go#L335-L347)

Below is the message reported by the analyzer for this snippet of code. Beware that the analyzer only reports the first
issue it finds, so please do not limit your consideration to the contents of the below message.

> reference to tknID is reassigned at line 336

[Click here to see the code in its original context.](https://github.com/Factom-Asset-Tokens/fatd/blob/f8331d1d63aad652e6ae481475458bb57a037f5b/cli/transact.go#L335-L347)

Click here to show the 13 line(s) of Go which triggered the analyzer.

```go
for tknID := range tkns {
params.NFTokenID = &tknID
err := FATClient.Request(context.Background(),
"get-nf-token", params, nil)
if err == nil {
errLog.Fatalf("invalid coinbase transaction: NFTokenID (%v) already exists",
tknID)
}
rpcErr, _ := err.(jsonrpc2.Error)
if rpcErr.Code != api.ErrorTokenNotFound.Code {
errLog.Fatal(err)
}
}

```

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See the descriptions of the classifications [here](https://github.com/github-vet/rangeclosure-findings#how-can-i-help) for more information.

commit ID: f8331d1d63aad652e6ae481475458bb57a037f5b