100 Go Mistakes.mdc

Go Best Practices

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Jun 17, 2026

Time

5 min

Difficulty

Beginner

Type

prompt

Package

Single file

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Contents

Skill content

Main instructions and any bundled files for this skill.

markdown

General Best Practices

Avoid variable shadowing.
Do not over-nest control flow (e.g., nested if or for blocks).
Avoid init() functions unless absolutely necessary.
Keep functions small and focused.
Prefer composition over inheritance (via embedding).
Use the functional options pattern for constructors where flexibility is needed.

Interfaces

Avoid defining interfaces until you need them.
Do not return interfaces from constructors or public APIs.
Define interfaces on the consumer side, not the producer side.
Keep interfaces small and focused (generally 1–2 methods).

Structs and Methods

Avoid embedding pointer types unless necessary.
Don’t overuse getters/setters — prefer public fields when it makes sense.
Use value receivers when the method doesn't mutate state or require pointer semantics.

Packages and Imports

Do not use util, common, or similarly vague package names.
Avoid package name collisions by using clear, unique names.
Do not expose unnecessary symbols (keep exported API minimal).

Slices

Distinguish between nil and empty slices.
Avoid memory leaks from slicing large arrays.
Always check the capacity when copying or appending slices.
Preallocate slice capacity when size is known ahead of time.

Maps

Always initialize maps before use.
Check existence with the two-value assignment (val, ok := m[key]).
Be aware that ranging over a map is in random order.

Error Handling

Always check errors — don’t ignore them.
Wrap errors with context when rethrowing.
Avoid panics except in truly unrecoverable cases.
Use errors.Is and errors.As for error comparison in Go 1.20+.

Goroutines and Concurrency

Always defer cancel() when using context.WithCancel.
Do not leak goroutines — ensure they exit cleanly.
Avoid data races — use mutexes or channels appropriately.
Never close a channel from the receiving side.

Testing and Debugging

Name tests consistently: TestXxx, BenchmarkXxx, ExampleXxx.
Use table-driven tests where possible.
Avoid global state in tests.
Use t.Helper() in helper functions to improve error tracebacks.

Code Style and Tools

Keep imports grouped and ordered: stdlib, external, internal.
Avoid magic numbers — use named constants.
Prefer explicit over implicit — especially in exported APIs.

Go 1.18+ Generics

Only use generics when they simplify code or add real flexibility.
Avoid over-engineering with type parameters.
Be cautious with constraint complexity — keep things readable.

Numbers and Types

Avoid using default int unless the size is appropriate.
Watch for integer overflows and underflows.
Avoid precision issues with float32/float64 — prefer math/big if needed.

Miscellaneous

Prefer any to interface{} in Go 1.18+, but avoid both unless necessary
Do not rely on map or slice comparison — use reflect.DeepEqual or a library.
Avoid relying on goroutine scheduling or map iteration order.

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