100 Go Mistakes and How to Avoid Them

Source code of 100 Go Mistakes and How to Avoid Them.

Table of Contents

Chapter 1 - Introduction

Chapter 2 - Code and Project Organization

• 1 - Unintended variable shadowing
• 2 - Writing nested code
• 3 - Misusing init functions
• 4 - Always using getters and setters
• 5 - Interface pollution
• 6 - Interface on the producer side
• 7 - Returning interfaces
• 8 - any says nothing
• 9 - Being confused about when to use generics
• 10 - Not being aware of the possible problems with type embedding
• 11 - Not using the functional options pattern
• 12 - Project misorganization (project structure and package organization)
• 13 - Creating utility packages
• 14 - Ignoring package name collisions
• 15 - Missing code documentation
• 16 - Not using linters

Chapter 3 - Data Types

• 17 - Creating confusion with octal literals
• 18 - Neglecting integer overflows
• 19 - Not understanding floating-points
• 20 - Not understanding slice length and capacity
• 21 - Inefficient slice initialization
• 22 - Being confused about nil vs. empty slice
• 23 - Not properly checking if a slice is empty
• 24 - Not making slice copy correctly
• 25 - Unexpected side-effects using slice append
• 26 - Slice and memory leaks
• 27 - Inefficient map initialization
• 28 - Map and memory leaks
• 29 - Comparing values incorrectly

Chapter 4 - Control Structures

• 30 - Ignoring that elements are copied in range loops
• 31 - Ignoring how arguments are evaluated in range loops (channels and arrays)
• 32 - Ignoring the impacts of using pointer elements in range loops
• 33 - Making wrong assumptions during map iterations (ordering and map insert during iteration)
• 34 - Ignoring how the break statement work
• 35 - Using defer inside a loop

Chapter 5 - Strings

• 36 - Not understanding the concept of rune
• 37 - Inaccurate string iteration
• 38 - Misusing trim functions
• 39 - Under-optimized strings concatenation
• 40 - Useless string conversion
• 41 - Substring and memory leaks

Chapter 6 - Functions and Methods

• 42 - Not knowing which type of receiver to use
• 43 - Never using named result parameters
• 44 - Unintended side-effects with named result parameters
• 45 - Returning a nil receiver
• 46 - Using a filename as a function input
• 47 - Ignoring how defer arguments and receivers are evaluated

Chapter 7 - Error Management

• 48 - Panicking
• 49 - Ignoring when to wrap an error
• 50 - Comparing an error type inaccurately
• 51 - Comparing an error value inaccurately
• 52 - Handling an error twice
• 53 - Not handling an error
• 54 - Not handling defer errors

Chapter 8 - Concurrency: Foundations

• 55 - Mixing concurrency and parallelism
• 56 - Concurrency isn't always faster
• 57 - Being puzzled about when to use channels or mutexes
• 58 - Not understanding race problems (data races vs. race conditions and Go memory model)
• 59 - Not understanding the concurrency impacts of a workload type
• 60 - Misunderstanding Go contexts

Chapter 9 - Concurrency: Practice

• 61 - Propagating an inappropriate context
• 62 - Starting a goroutine without knowing when to stop it
• 63 - Not being careful with goroutines and loop variables
• 64 - Expecting a deterministic behavior using select and channels
• 65 - Not using notification channels
• 66 - Not using nil channels
• 67 - Being puzzled about a channel size
• 68 - Forgetting about possible side-effects with string formatting (etcd and dead-lock)
• 69 - Creating data races with append
• 70 - Using mutexes inaccurately with slices and maps
• 71 - Misusing sync.WaitGroup
• 72 - Forgetting about sync.Cond
• 73 - Not using errgroup
• 74 - Copying a sync type

Chapter 10 - Standard Library

• 75 - Providing a wrong time duration
• 76 - time.After and memory leak
• 77 - JSON handling common mistakes
  • Unexpected behavior because of type embedding
  • JSON and monotonic clock
  • Map of any
• 78 - SQL common mistakes
  • Forgetting that sql.Open doesn't necessarily establish connections to a DB
  • Forgetting about connections pooling
  • Not using prepared statements
  • Mishandling null values
  • Not handling rows iteration errors
• 79 - Not closing transient resources (HTTP body, sql.Rows, and os.File)
• 80 - Forgetting the return statement after replying to an HTTP request
• 81 - Using the default HTTP client and server

Chapter 11 - Testing

• 82 - Not categorizing tests (build tags and short mode)
• 83 - Not enabling the race flag
• 84 - Not using test execution modes (parallel and shuffle)
• 85 - Not using table-driven tests
• 86 - Sleeping in unit tests
• 87 - Not dealing with the time API efficiently
• 88 - Not using testing utility packages (httptest and iotest)
• 89 - Writing inaccurate benchmarks
  • Not resetting or pausing the timer
  • Making wrong assumptions about micro-benchmarks
  • Not being careful about compiler optimizations
  • Being fooled by the observer effect
• 90 - Not exploring all the Go testing features
  • Code coverage
  • Testing from a different package
  • Utility functions
  • Setup and teardown

Chapter 12 - Optimizations

• 91 - Not understanding CPU caches
  • CPU architecture
  • Cache line
  • Slice of structs vs. struct of slices
  • Predictability
  • Cache placement policy
• 92 - Writing concurrent code leading to false sharing
• 93 - Not taking into account instruction-level parallelism
• 94 - Not being aware of data alignment
• 95 - Not understanding stack vs. heap
• 96 - Not knowing how to reduce allocations
  • API change
  • Compiler optimizations
  • sync.Pool
• 97 - Not relying on inlining
• 98 - Not using Go diagnostics tooling (profiling and execution tracer)
• 99 - Not understanding how the GC works
• 100 - Not understanding the impacts of running Go inside of Docker and Kubernetes