Common the blank identifier mistakes
Fast recall
Quick revision
Core answer
_ to silence an error. The code may continue with a zero or partial result and fail later, far from the real cause. Name and handle errors, keep _ for truly irrelevant values, and add a comment when a side-effect import or deliberate discard is not obvious.Name a concrete the blank identifier mistake, show its visible effect, and explain how to prevent and test it.
Saying only “be careful” without tracing the incorrect behaviour.
Show the smallest failing example and the regression test that protects the rule.
Interview-ready guide
Interview answer
The blank identifier is written as
_. It receives a value and immediately discards it, which lets Go code intentionally ignore a return value or one value produced byrange._is not a normal variable: its value cannot be read later. It should communicate that a value is deliberately unused, not hide information the program should handle.The dangerous mistake is using
_to silence an error. The code may continue with a zero or partial result and fail later, far from the real cause. For example: Ifstrconv.Atoi("bad")has its error discarded, the returned integer is zero. The program may treat invalid input as a genuine zero instead of rejecting it.A blank import such as
_ "net/http/pprof"runs a package's initialization for side effects. This is different from discarding a normal value and should be rare and documented. This is why the surrounding data contract matters as much as the syntax.Name and handle errors, keep
_for truly irrelevant values, and add a comment when a side-effect import or deliberate discard is not obvious. Test invalid input as well as valid input, and assert that the original error is returned or wrapped instead of silently becoming a zero result.
Common the blank identifier mistakes
Direct Answer
The dangerous mistake is using _ to silence an error. The code may continue with a zero or partial result and fail later, far from the real cause. Name and handle errors, keep _ for truly irrelevant values, and add a comment when a side-effect import or deliberate discard is not obvious.
Deep Dive & Architecture
When a valid-looking zero appears unexpectedly, search for discarded errors or values near parsing, I/O, type assertions, and database calls.
Restore the named value and handle it at the source.
Check every multi-value call that uses _, range loops that may need the missing index, and blank imports that change program startup. Test invalid input as well as valid input, and assert that the original error is returned or wrapped instead of silently becoming a zero result.
The dangerous mistake is using _ to silence an error. The code may continue with a zero or partial result and fail later, far from the real cause. Name and handle errors, keep _ for truly irrelevant values, and add a comment when a side-effect import or deliberate discard is not obvious.
Code Example
n, err := strconv.Atoi(input)
if err != nil {
return fmt.Errorf("invalid number %q: %w", input, err)
}
return use(n)
Common Mistakes & Pitfalls
Saying only “be careful” without tracing the incorrect behaviour.
Check your understanding
Answer these without looking back at the article.
- What are the blank identifier in Go, and how do they work?
- How do the blank identifier compare with a named variable in Go?
- When should you use the blank identifier in Go?
Looking for a structured roadmap?
Every module on this page is also part of the full Java backend interview track.