TwistoPayments/userd: main.go; 11 LoC

Found a possible issue in [TwistoPayments/userd](https://www.github.com/TwistoPayments/userd) at [main.go](https://github.com/TwistoPayments/userd/blob/cd4a73147b6de78a5a4f0eb6dcef01411a55dfd2/main.go#L188-L198)

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 u is reassigned at line 191

[Click here to see the code in its original context.](https://github.com/TwistoPayments/userd/blob/cd4a73147b6de78a5a4f0eb6dcef01411a55dfd2/main.go#L188-L198)

Click here to show the 11 line(s) of Go which triggered the analyzer.

```go
for _, u := range systemUsers {
directoryUser, present := directoryUsers[u.Username]
if !present {
directoryUsers[u.Username] = &u
} else {
log.Fatalf(
"User %s defined both in directory and in systemUsers.\nDirectory definition: %#v\n",
u.Username, directoryUser,
)
}
}

```

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commit ID: cd4a73147b6de78a5a4f0eb6dcef01411a55dfd2