In addition to simply storing messages from your applications, you can create application panics and fatal errors that will prevent the application from continuing. This is critical for any use case where errors that do not halt execution lead to potential security issues, data loss, or any other unintended consequence. These types of mechanisms are generally relegated to the most critical of errors.

When to use a panic() method is not always clear, but in practice this should be relegated to errors that are unrecoverable. An unrecoverable error typically means the one where state becomes ambiguous or cannot otherwise be guaranteed.

For example, operations on acquired database records that fail to return expected results from the database may be considered unrecoverable because future operations might occur on outdated or missing data.

In the following example, we can implement a panic where we can't create a new user; this is important so that we don't attempt to redirect or move forward with any further creation steps:

  if err != nil {
    fmt.Fprintln(w, err.Error)
    RegError.Println("Could not complete registration:", err.Error)
    panic("Error with registration,")
  } else {
    http.Redirect(w, r, "/page/"+pageGUID, 301)
  }

Note that if you want to force this error, you can just make an intentional MySQL error in your query:

  res, err := database.Exec("INSERT INTENTIONAL_ERROR INTO users SET user_name=?, user_guid=?, user_email=?, user_password=?", name, guid, email, passwordEnc)

When this error is triggered you will find this in your respective log file or stdout:

In the preceding example, we utilize the panic as a hard stop, one that will prevent further execution that could lead to further errors and/or data inconsistency. If it need not be a hard stop, utilizing the recover() function allows you to re-enter application flow once the problem has been addressed or mitigated.