Get error code number from postgres in Go

This is written in the documentation. As you see you can extract it in this way:

if err, ok := err.(*pq.Error); ok {
    fmt.Println(err.Code)
}

Do not forget to remove the underscore from your import _ "github.com/lib/pq". As you see err has a lot of information about the error (not only Code but many others).

Notice that you can't compare it directly to some code (it is of ErrorCode type).

So you have to convert it to string and compare against a string.

https://godoc.org/github.com/lib/pq#Error

You need to type assert the error to the type *pq.Error:

pqErr := err.(*pq.Error)
log.Println(pqErr.Code)