# Go Nil Pointer

> Pointer receiver nil safety - methods can be called on nil Use when this capability is needed.

- Skill: `tomevault-io/go-nil-pointer` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/go-nil-pointer`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/go-nil-pointer/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/go-nil-pointer

---


# Pointer Receiver Nil

## Problem
Methods with pointer receivers can be called on nil. Must handle nil receiver.

## Pattern

### WRONG - Assume receiver is non-nil
```go
type Tree struct {
    Value int
    Left  *Tree
}

func (t *Tree) Sum() int {
    return t.Value + t.Left.Sum()  // PANIC if t or t.Left is nil
}
```

### CORRECT - Handle nil receiver
```go
type Tree struct {
    Value int
    Left  *Tree
    Right *Tree
}

func (t *Tree) Sum() int {
    if t == nil {
        return 0  // Nil tree has sum of 0
    }
    return t.Value + t.Left.Sum() + t.Right.Sum()
}

// Now safe to call
var tree *Tree  // nil
sum := tree.Sum()  // Returns 0, no panic
```

## Use Cases
Nil receiver pattern enables elegant recursive algorithms and optional behavior.

## Quick Fix
- [ ] Check if receiver is nil at method start
- [ ] Define sensible zero behavior for nil receiver
- [ ] Document whether methods are nil-safe

## When NOT to Use
If nil receiver doesn't make semantic sense, panic early with clear message.

---
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<!-- tomevault:4.0:skill_md:2026-04-13 -->