Go language foundation ----- 01 ----- go language features

One go Linguistic characteristics

1.1 Development environment construction

It's actually installation go Environment and GoLand IDE Tools .
go Language environment ：go Locale download address .
You need to pay attention to this download ： First, use the following command to view the corresponding win System architecture , Select the corresponding version , Otherwise, in the vscode When downloading plug-ins ,dlv And dlv-map Will not be able to download .

echo %PROCESSOR_ARCHITECTURE%
# perhaps echo %PROCESSOR_IDENTIFIER% 、systeminfo. Here I use the first direct view is AMD64 framework 

So in choosing windows Software package for , You have to choose to have amd Situation of words , And choose msi Suffix , This means that you can directly install , No other steps are needed .

GoLand IDE Tools ：GoLand IDE Tool download address . However, this version that you want to crack needs a compressed package .

stay debug front , It's best to execute the following command first , Prevent the influence mod Project .

go env -w GO111MODULE=off

stay vscode Conduct debug, After installing all plug-ins , I want to debug, however vscode Has been an error , Error is as follows ：

unable to locate "go" binary in GOROOT () or PATH(xxx)

It probably means that there is no corresponding go.exe Binary , But I'm directly in cmd above go env It works , And I clearly see the system of environment variables Path notice GOROOT The path of . I thought it was GOPATH Under the src Cannot exist alone xxx.go file , But when I'm done , It's no problem to put it alone . So the question should be ： Or vscoe The problem of , Or go Own path problem .

I solved it like this ： New on desktop go_src Catalog , Create a subdirectory inside src.src add to test.go file , And then " desktop \go_src" Add path to GOPATH In the environment variables . Use vscode again debug, Then you can succeed debug 了 .

Then continue to want to repeat the above problem , But the same directory architecture and debug The way , It works , So this mistake is either a guess or vscoe The problem of , Or go Own path problem .

go stay vscode Of debug Than C++ Simple , Click Run , Then it will fail , Because you didn't create it for the first time launch.json file , Directly click to create without changing the content debug 了 .

1.2.1 Go Linguistic characteristics - Garbage collection

• a. Automatic memory recycling , No more developers managing memory .
• b. Developers focus on business implementation , It reduces the mental burden .
• c. It only needs new Allocate memory , No need to release .
• d. gc Garbage collection 4ms.

1.2.2 Go Linguistic characteristics - Natural concurrence

• a. Support concurrency from the language level , It's simple .
• b. goroute, Lightweight threads , Create thousands of goroute Make it possible .
• c. be based on CSP（Communicating Sequential Process） Model implementation .
  Test code ：

// goroute.go
// 1.  A file belongs to a package , This indicates that this file belongs to main This package , A package can have multiple files .
package main

// 2.  Import other libraries . If the package is not used ,go Will report a mistake , Strict grammar .
import (
	"fmt"
)

// 3.  The functions of the package 
func test_goroute(a int) {
    
	fmt.Println(a)
}

// main.go
// 4.  Note the need for main The directory execution of the upper layer of the function is E:\go_study\go_code\1-src\src\1：go run .\1-1-goroute\
//  Otherwise it will fail 
package main

import (
	"time"
)

func main() {
    

	// 5.  Start a hundred collaborative processes .go The keyword represents the starting process .
	// go The process of cooperation in is ： Open up in a thread , When opening up multiple collaborative processes , They do not interfere with each other , All are executed asynchronously . So printing can see that the order is disordered .
	for i := 0; i < 100; i++ {
    
		go test_goroute(i)
	}

	//  sleep 1 second 
	time.Sleep(time.Second)
}

1.2.3 Go Linguistic characteristics -channel

• a. The Conduit , similar unix/linux Medium pipe, fifo , One end is reading, and the other end is writing ,channel It's process safe , There will be a lock inside . And previous C Language synergy comparison , A thread can run multiple coprocedures , But there is no race relationship ,1:n The relationship between , It is safe for multiple coroutines to access global variables , It can be considered that one thread polls multiple threads . and go Between threads and coroutines of m:n Relationship , There is a race relationship .
• b. Multiple goroute Through between channel communicate .
• c. Support any type .

Code testing ：

package main

import "fmt"

func test_pipe() {
    
	pipe := make(chan int, 3)
	pipe <- 1
	pipe <- 2
	pipe <- 3
	var t1 int
	t1 = <-pipe
	fmt.Println("t1: ", t1)

}

func sum(s []int, c chan int) {
    
	//test_pipe()
	sum := 0
	for _, v := range s {
    
		sum += v
	}
	fmt.Println("sum:", sum)
	c <- sum // send sum to c
}

func main() {
    
	// 1.  Defining slices s
	s := []int{
    7, 2, 8, -9, 4, 0}
	// 2.  Create channels c
	c := make(chan int)
	// 3.  Pass the first half of the slice elements and channels into the coroutine , Cumulative sum of processes , then push To the passage .
	go sum(s[:len(s)/2], c) // 7+2+8 = 17, -9 + 4+0 = -5
	// 4.  Empathy , Transfer the elements and channels of the second half of the slice into the coroutine , Cumulative sum of processes , then push To the passage .
	go sum(s[len(s)/2:], c)

	// 5.  At this time, the channel should have two statistical values . Let's get , Follow the first in, first out rule of the channel .
	// x, y := <-c, <-c // receive from c
	x := <-c
	y := <-c
	fmt.Println(x, y, x+y)
}

result ：

1.2.4 Go Linguistic characteristics - Multiple return values

go A function of returns multiple values , similar lua.

Test code ：
My directory structure is like this , Use up to four go file .add.go、calc.go、sub.go、main.go.

// add.go
package calc


func Add(a int, b int) int {
    
	return a + b
}

// calc.go
package calc

func Calc(a int, b int)(int,int) {
    
    sum := a + b
    avg := (a+b)/2
    return sum, avg
}

// sub.go
package calc

func Sub(a int, b int) int {
    
	return a - b
}

// main.go
package main

//  Because I'm here GOPATH Set up E:\go_study\go_code\1-src For environment variables , and go It will automatically find src Catalog ,
//  So below import calc Packet time , Its path is ："1/1-3-package/calc".
//  But note that sometimes after adding environment variables , It doesn't take effect immediately , You may need to wait .
import (
	"1/1-3-package/calc"
	"fmt"
)

func main() {
    
	sum := calc.Add(100, 300)
	sub := calc.Sub(100, 300)

	fmt.Println("sum=", sum)
	fmt.Println("sub=", sub)

	sum, avg := calc.Calc(100, 300)
	fmt.Println("sum=", sum)
	fmt.Println("avg=", avg)
}

result ：

1.3 first golang Program

It's printing hello woeld, It's not shown here .

1.4.1 The concept of a package

1. and python equally , Put the code of the same function into a directory , Call it a bag .
2. Packages can be referenced by other packages .
3. main Packages are used to generate executable files , There is only one per program main package .
4. The main purpose of the package is to improve the reusability of the code .

1.4.2 The actual combat of Bao

That is, how to reference your own package , Look back to the above 1.2.4 Go Linguistic characteristics - Examples of multiple return values are sufficient .

Two summary

• 1） This section is mainly about go How to install the environment and related syntax , How to compile and run , And related concepts .