knowledge/categories/go.md

Language

pass pointer or value

• value: Variable must not be modified
• Variable is a large struct then prefer pointer
• Variable is a map or slice then prefer value
• Passing by value often is cheaper

struct

• make
  • make(T, args) -> T
• new
  • new(T) -> *T
• a := T{}

Slice

• Auto scale length
  • new([]int)
  • make([]int, 2, 5)

Go routine

• you can run more goroutine vs thread
• go routine have a fater startup time than thread
• go routine come with built-in primitives to communicate safely by using channels

Closure

Channel

• messages := make(chan string) // Send a value into a channel using the channel <- go func() { messages <- "ping" }() // channel. Here we'll receive the "ping" message msg := <-messages

• buffered channel

  • ch := make(chan Task, 3)

Sync

• atomic
• Mutex
  • sync.Mutex()
  • mutex.Lock()
  • mutx.Unlock()
• string literals
  • `aaa bbb ccc`
• panic / recover

Frameworks

db

• xorm
• gorm

web

• beego
• mux
• gin
• go kit
  • full stack micro service framework like spring boot

tools

• profiler
  • go-wrk(wrk)
    • a http benchmark tool
  • go-torch
    • Stochastic flame graph profiler
• test
  • github.com/stretchr/testify

Tips

slice

• byte* array //actual data
• uintgo len
• uintgo cap

map

• implement by hash table

Go has no generics

• performance
• complexity
• If C++ and Java are about type hierarchies and the taxonomy of types, Go is about composition.
• How to solve
  • use interface
  • use type assertions
  • use reflection

Modify item in range

• use the array index instead of the value

    for _, e := range array {
        e.field = "foo"
    }

    for idx, _ := range array {
        array[idx].field = "foo"
    }

merge two array

• a = append(a, b…)
  • must add … to b, otherwise you can only add one item

error handling

• error type assertion

  • if serr, ok := err.(*json.SyntaxError); ok {}

• better error handling

  • custom error type

    • type appError struct { Error error Message string Code int }

  • concat error check

    • if err1() != nil || err2() != nil {}

  • some error constants

    • errNotFound = errors.New("Item not found") switch err { case errNotFound: }

date format

• t := time.Now() fmt.Println(t.String()) fmt.Println(t.Format("2006-01-02 15:04:05"))

• var _ InterfaceX = &InterfaceXImplementation{}

  • make sure InterfaceX’s implementation works

commands

test

• go test ./...
  •  run all tests in current directory and all of its subdirectories
• go test foo/...
  •  run all tests with import path prefixed with foo/:
• go test foo...
  • run all tests import path prefixed with foo:
• go test ...
  • run all tests in your $GOPATH: