new check: time.Add with unused return value

[tux21b]

Hi, thanks for your great work. A common error in our code base that happens over and over again is something like that:

t := time.Now()
t.Add(1 * time.Hour)
fmt.Println(t)

Since time.Time is a "value type", Add() does not modify the current value and returns a new time object, which is unused in the code above. Calling time.Add() without using the return value is always an error.

There are probably lots of similar functions in the standard library. The same check might be used to for time.In, strings.ToLower and strings.ToUpper as well.

Are you interested in a check like that, how should it be called and should I try to prepare a MR for it?

[dominikh]

We already have SA4017 for flagging calls like that. It should be a simple matter of extending the list of functions it looks for.

I'll put it on my todo list. To be very frank, a PR would probably be more work for me than just making the change.