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I'm pretty new to golang so sorry for my question. I have the following function:

func (app *application) serverError(w http.ResponseWriter, err error) {
  trace := fmt.Sprintf("%s\n%s", err.Error(), debug.Stack())
  app.errorLog.Output(2, trace)
  http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
I'm using golangci-lint linter, and when I launch the linter, it returns the following error:
cmd/web/helpers.go:15:22: Error return value of `app.errorLog.Output` is not checked (errcheck)
  app.errorLog.Output(2, trace)
How can I fix that?
In go, a common pattern is to have a function that returns two values, the first of which is the desired result, and the second of which is type error.
Typically, if an implementation cannot provide a value because of some error e, it will return nil, e or return <zero value for type>, e.
It doesn't just have to be one such desired result value, however - sometimes there will be zero or more than one desired result values.  Basic rule: if the last return value of a function is error typed, and the docs don't say otherwise, always check that last return value.
So, when you see such a pattern in a return signature - you should not discard the last result with a ignored return or an assign to '_', but should check that value to make sure it is non-nil before continuing.
The first of those anti-patterns is what the linter is warning you about.  You can check the error argument thusly (I'm assuming that there are zero "desired result" values here):
 if err := app.errorLog.Output(2, trace); err != nil {
     // ... do something to handle error here or panic(err)
This will satisfy the linter and make your code more robust!
                If there were one non-error return value, and you wanted to ignore it, you'd say if _, err := app.errorLog.Output(2, trace); err != nil { ...
– BadZen
                Jun 21, 2021 at 20:05
        
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