Mastering Go学习笔记

起始于2021-05-15，持续更新，环境为Windows 10 21H2。其中Chapter7为翻译内容，欢迎大家围观 Mastering Go Second Edition中文版

Chapter 1 Go and the Operating System

Some fact

• Go 起源于2009，Made By Google
• Go2 is developing
• Go uses static linking by default and builds into executable binary
• Go supports Unicode
• Go do not do preprocessing

安装

choco install golang
go env -w GOPROXY=https://goproxy.cn #这一步是翻墙
## Create a folder
go mod init YOUR_MODULE_NAME

Hello World Programme

Create a folder name chapter_1

package main

import (
	"fmt"
)

func main() {
	fmt.Println("Hello World")
}

build and run

go build .\chapter_1\aSourceFile.go
.\aSrouceFile.exe

> Hello World

注意naming convention 不应该是 aSourceFile.go 应该是 source_file.go
如果不想compile就启动的话

go run source_file.go

> Hello World

STDOUT

optput:

fmt.Println(s1,s2) == fmt.Print(s1, " ", s2, "\n")

Variable

The official name for := is the short assignment statement.

Command Line Argument

func main() { 
	if len(os.Args) == 1 {
		fmt.Println("Please give one or more floats.") os.Exit(1)
	} 
	arguments := os.Args
	min, _ := strconv.ParseFloat(arguments[1], 64)
	max, _ := strconv.ParseFloat(arguments[1], 64)

argument[0] = programme name
argumeent[1..] = arguments in string form

Chapter 2 Understanding Go Internals

Compiler

To compile go programm

go tool compile test.go
go tool compile -pack test.go -> you will get an archive file instead of an object file, an archive file is used to group multiple files

GC

To observe memory statistics

var mem runtime.MemStats 
runtime.ReadMemStats(&mem)
fmt.Println("mem.Alloc:", mem.Alloc)
fmt.Println("mem.TotalAlloc:", mem.TotalAlloc)
fmt.Println("mem.HeapAlloc:", mem.HeapAlloc)
fmt.Println("mem.NumGC:", mem.NumGC)
fmt.Println("-----")

Go uses Tricolor Sweeping Algo to carry out GC: The objects of the black set are guaranteed to have no pointers to any object of the white set; Grey color set might have reference to white set.

首先color ROOT reference to grey -> The roots are the objects that can be directly accessed by the application, which includes global variables and other things on the stack. -> pick grey变成黑色 -> 递归寻找黑色的dependent改成灰色（如果是白色的话）-> 直到所有的灰色都被遍历过就okleh -> 回收白色

Using C Languang

package main 

//#include <stdio.h>
//void callC() {
//	printf("Calling C Code!/n")
//} 

import "C"
import "fmt" 

func main() {  
	fmt.Println("A Go statement!")   
	C.callC()  
	fmt.Println("Another Go statement!")
}

DEFER

# 1 2 3
func d1() {
	for i := 3; i > 0; i-- { 
		defer fmt.Print(i, " ")
	}
}

# 0 0 0
func d2() { 
	for i := 3; i > 0; i-- { 
		defer func() {
			fmt.Print(i, " ") 
		}() 
	} 
	fmt.Println()
}

# 1 2 3
func d3() { 
	for i := 3; i > 0; i-- { 
		defer func(n int) { 
			fmt.Print(n, " ")
		}(i) 
	}
}

defer keyword is last in first out.