Go、または Golang は、Google によって開発されたオープンソース プログラミング言語です。これは、スケーラブルで高性能なアプリケーションを構築するために静的に型付け、コンパイル、設計されています。
Goroutine は、Go ランタイムによって管理される軽量のスレッドです。これらは、他の関数またはメソッドと同時に実行される関数またはメソッドです。
関数呼び出しの前に go キーワードを使用します。
go myFunction()
チャネルは、ゴルーチンが相互に通信し、実行を同期するための方法です。値の送受信が可能です。
ch := make(chan int)
バッファされたチャネルには指定された容量があり、バッファがいっぱいになるまで値を送信できます。受信機が受信できる状態になっている必要はありません。
close() 関数を使用します:
close(ch)
構造体は、さまざまなデータ型のフィールドを 1 つのエンティティにグループ化できるユーザー定義型です。
type Person struct {
Name string
Age int
}
Go のインターフェイスは、メソッド シグネチャのセットを指定する型です。動作を定義することでポリモーフィズムが可能になります。
型は、そのすべてのメソッドを実装することによってインターフェイスを実装します。
type Animal interface {
Speak() string
}
type Dog struct{}
func (d Dog) Speak() string {
return "Woof!"
}
defer は、周囲の関数が戻るまで関数の実行を延期するために使用されます。
遅延関数は LIFO (後入れ先出し) 順序で実行されます:
defer fmt.Println("world")
fmt.Println("hello")
// Output: hello world
ポインタは値のメモリアドレスを保持します。値をコピーする代わりに参照を渡すために使用されます。
var p *int p = &x
スライスは、要素のシーケンスをより柔軟に操作する方法を提供する、動的にサイズが変更される配列です。
s := make([]int, 0)
マップはキーと値のペアのコレクションです。
m := make(map[string]int)
select を選択すると、Goroutine が複数の通信操作を待機できるようになります。
select {
case msg := <-ch:
fmt.Println(msg)
default:
fmt.Println("No message received")
}
nil チャネルは送信操作と受信操作の両方をブロックします。
init は、パッケージレベルの変数を初期化する特別な関数です。 main の前に実行されます。
はい、ただし、表示される順序で実行されます。
空の構造体はストレージをゼロバイト消費します。
エラー タイプを返し、以下を使用してチェックします。
if err != nil {
return err
}
型アサーションは、インターフェイスの基礎となる値を抽出するために使用されます:
value, ok := x.(string)
go fmt 標準スタイルに従って Go ソース コードをフォーマットします。
go mod は Go プロジェクトのモジュールの依存関係を管理します。
go mod init module-name
パッケージは、関連する Go ファイルをグループ化する方法です。
import "fmt"
panic is used to terminate the program immediately when an error occurs.
recover is used to regain control after a panic.
It is used inside a deferred function:
defer func() {
if r := recover(); r != nil {
fmt.Println("Recovered:", r)
}
}()
Constants are immutable values declared using the const keyword.
const Pi = 3.14
iota is a constant generator that increments by 1 automatically.
go test is used to run unit tests written in Go.
Test functions must start with Test:
func TestAdd(t *testing.T) {
result := Add(2, 3)
if result != 5 {
t.Errorf("expected 5, got %d", result)
}
}
Benchmarking is used to measure the performance of a function using go test.
Benchmark functions must start with Benchmark:
func BenchmarkAdd(b *testing.B) {
for i := 0; i < b.N; i++ {
Add(2, 3)
}
}
Build constraints are used to include or exclude files from the build process based on conditions.
Place the constraint in a comment at the top of the file:
// +build linux
Slices are built on top of arrays and provide a dynamic view over the array.
Go automatically manages memory using garbage collection, which frees up memory that is no longer in use.
The context package is used for managing deadlines, cancellation signals, and request-scoped values. It helps in controlling the flow of Goroutines and resources.
ctx, cancel := context.WithTimeout(context.Background(), time.Second) defer cancel()
sync.WaitGroup is used to wait for a collection of Goroutines to finish executing.
var wg sync.WaitGroup
wg.Add(1)
go func() {
defer wg.Done()
// Do some work
}()
wg.Wait()
sync.Mutex provides a lock mechanism to protect shared resources from concurrent access.
var mu sync.Mutex
mu.Lock()
// critical section
mu.Unlock()
select is used to handle multiple channel operations simultaneously, allowing a Goroutine to wait for multiple communication operations.
go generate is a command for generating code. It reads special comments within the source code to execute commands.
Method receivers specify the type the method is associated with, either by value or pointer:
func (p *Person) GetName() string {
return p.Name
}
Variadic functions accept a variable number of arguments:
func sum(nums ...int) int {
total := 0
for _, num := range nums {
total += num
}
return total
}
A rune is an alias for int32 and represents a Unicode code point.
A select block without a default will block until one of its cases can proceed.
A ticker sends events at regular intervals:
ticker := time.NewTicker(time.Second)
Use the encoding/json package to marshal and unmarshal JSON:
jsonData, _ := json.Marshal(structure)
json.Unmarshal(jsonData, &structure)
go vet examines Go source code and reports potential errors, focusing on issues that are not caught by the compiler.
An anonymous function is a function without a name and can be defined inline:
func() {
fmt.Println("Hello")
}()
time.Duration represents the elapsed time between two points and is a type of int64.
Use context.WithTimeout to set a timeout:
ctx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()
A pipeline is a series of stages connected by channels, where each stage is a collection of Goroutines that receive values from upstream and send values downstream.
pkg is a directory used to place reusable packages. It is a common convention but not enforced by Go.
Use tools like dlv (Delve), print statements, or the log package.
type aliasing allows you to create a new name for an existing type:
type MyInt = int
slice1 := []int{1, 2}
slice2 := []int{3, 4}
copy(slice2, slice1) // [1, 2]
go doc is used to display documentation for a Go package, function, or variable.
Use recover to gracefully handle panics and log them for debugging:
defer func() {
if r := recover(); r != nil {
log.Println("Recovered from:", r)
}
}()
The unsafe package allows low-level memory manipulation. It is not recommended for regular use.
Use interfaces and constructor functions to pass dependencies, allowing easy mocking and testing.
type HttpClient interface{}
func NewService(client HttpClient) *Service {
return &Service{client: client}
}
A Goroutine is a lightweight thread managed by the Go runtime. It differs from OS threads as it uses a smaller initial stack (2KB) and is multiplexed onto multiple OS threads. This makes Goroutines more efficient for handling concurrency.
The Go scheduler uses a work-stealing algorithm with M:N scheduling, where M represents OS threads and N represents Goroutines. It schedules Goroutines across available OS threads and CPUs, aiming to balance workload for optimal performance.
A memory leak occurs when allocated memory is not released. In Go, it can happen if Goroutines are not terminated or references to objects are kept unnecessarily. Use defer for cleanup and proper cancellation of Goroutines to prevent leaks.
Go uses a concurrent, mark-and-sweep garbage collector. It identifies reachable objects during the mark phase and collects the unreachable ones during the sweep phase, allowing other Goroutines to continue running during collection.
Race conditions occur when multiple Goroutines access a shared variable concurrently without proper synchronization. Use go run -race to detect race conditions in Go programs.
Struct tags provide metadata for struct fields, often used for JSON serialization:
type User struct {
Name string `json:"name"`
Age int `json:"age"`
}
Create a custom error by implementing the error interface:
type MyError struct {
Msg string
}
func (e *MyError) Error() string {
return e.Msg
}
A nil pointer dereference occurs when you attempt to access the value a nil pointer points to. Avoid this by checking for nil before using pointers.
sync.Pool is used for reusing objects and reducing GC pressure. It provides a way to cache reusable objects, unlike the GC which automatically frees unused memory.
Use channels to distribute tasks and manage worker Goroutines:
jobs := make(chan int, 100)
for w := 1; w <= 3; w++ {
go worker(w, jobs)
}
The reflect package allows runtime inspection of types and values. It is used for dynamic operations like inspecting struct fields or methods.
Ensure Goroutines are terminated using context for cancellation or using timeouts with channels.
io.Reader has a Read method for reading data, while io.Writer has a Write method for writing data. They form the basis of Go's I/O abstractions.
A nil value interface is an interface with a nil underlying value. It can cause unexpected behavior when check nil, as an interface with a nil underlying value is not equal to nil.
type MyInterface interface{}
var i MyInterface
var m map[string]int
i = m // This case, m is nil but i not nil
To handle above case, we could use interface assertion as following
if v, ok := i.(map[string]int); ok && v != nil {
fmt.Printf("value not nil: %v\n", v)
}
To prevent deadlocks, ensure that:
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