zengfu/mqtt_broker: session.go; 3 LoC

Found a possible issue in [zengfu/mqtt_broker](https://www.github.com/zengfu/mqtt_broker) at [session.go](https://github.com/zengfu/mqtt_broker/blob/015caf7439ec5baa14027d7b1440ef3ffca1cd1b/session.go#L125-L127)

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.

>

[Click here to see the code in its original context.](https://github.com/zengfu/mqtt_broker/blob/015caf7439ec5baa14027d7b1440ef3ffca1cd1b/session.go#L125-L127)

Click here to show the 3 line(s) of Go which triggered the analyzer.

```go
for _, sub := range subscriptions {
db.Delete(&sub)
}

```

Click here to show extra information the analyzer produced.

```
No path was found through the callgraph that could lead to a function which writes a pointer argument.

No path was found through the callgraph that could lead to a function which passes a pointer to third-party code.

root signature {Delete 1} was not found in the callgraph; reference was passed directly to third-party code
```

Leave a reaction on this issue to contribute to the project by classifying this instance as a **Bug** :-1:, **Mitigated** :+1:, or **Desirable Behavior** :rocket:
See the descriptions of the classifications [here](https://github.com/github-vet/rangeclosure-findings#how-can-i-help) for more information.

commit ID: 015caf7439ec5baa14027d7b1440ef3ffca1cd1b

Read session.go at lines 125-127 and inspect the shown call to db.Delete in its original context. Decide whether the analyzer finding should be classified as Bug, Mitigated, or Desirable Behavior, then leave the corresponding reaction on the issue; completion is the recorded classification.

Written by the indexing model from the issue text.