First, share an operation that allows you to view documents locally （linux System ）

1. Open command line terminal , Input godoc -http=:8000, If you want to run in the background, add a &

2. Then open the browser , Enter url ：localhost:8000 You can have a good time reading the document

go What is language? I don't think I need to introduce it ～～～ Let's go to Baidu

Next I'll knock one step at a time hello who？ Code

download

If you're using linux System ：

sudo apt-get install golang

If it doesn't work ：

sudo add-apt-repository ppa:gophers/go
sudo apt-get update
sudo apt-get install golang

If you're using windows,mac System ：

Check Baidu ～～～

Execute at the terminal go version

If you fail , Let's see how to configure environment variables

by GOPATH To prepare for

GOPATH Yes Go It's a very important environment variable for me , Before setting environment variables , We need to do some preparatory work first

Create a folder where you like , You can call it whatever you want , I was built in /home/username In the directory , The name of the folder is go. Under this folder, create 3 A folder , The names are /bin,/pkg,/src./src Put the source code , Use go get On command , The source code is downloaded in this folder ./bin Storage and use go install Command compiled executable ./pkg Store the generated file after compilation （ The role of this directory is my baidu …… I don't know how to use it , After all, beginners 0.0） thus , Preparatory work completed .

Set the environment variable

stay /etc/profile perhaps ~/.profile Add these lines to the list

export GOROOT=/usr/lib/go
export GOPATH=/home/username/go（ It depends here , Look where your folder is ）
export PATH=                            P                    A                    T                    H                    :                         PATH:              PATH:GOPATH/bin（ After adding this environment variable ,go install The generated executable file can be executed anywhere 0.0）

then , Type this code into the terminal , Make the configuration work

source .profile（ It depends on which file you changed , This file is only for a specific individual user , That is to say, it only works for one user ）

then , Input... At the terminal go env

You can see everything go Related environment variables

Knock on the code ！

stay $GOPATH/src Under the table of contents , New name is hello Folder , Create a new hello.go Source code file for

Start typing code ！！！

package main

func main() {
who := “world!”
if len(os.Args[1:]) > 0 {
who = “”
for _, arg := range os.Args[1:] {
who += " " + arg
}
}
fmt.Println(“hello”, who)
}
It's hard to see the code ？ Do you think blogger's code format is poisonous ？ take it easy , So let's look down .
go The tool chain of language is very powerful , One of them is called goimports Tools for （ Science popularization is a tool ：gorun, You can put go Language runs as a scripting language ）

If you don't install it, post the install command below ：

sudo apt-get install golang-golang-x-tools

Then execute the following command ：

goimports -w hello.go

-w Parameter is used to write the result to a file , Instead of the output at the terminal , Take a look at the code now

package main

import (
“fmt”
“os”
)

func main() {
who := “world!”
if len(os.Args[1:]) > 0 {
who = “”
for _, arg := range os.Args[1:] {
who += " " + arg
}
}
fmt.Println(“hello”, who)
}

hohoho, I swear I didn't touch the source file ～～～
gofmt There's also the ability to normalize code , It's just goimports Tools are more powerful , You can automatically import the packages you need （Go Language is delicate , If the package is imported but not used or the package used is not imported, the compilation will fail ）

function

Get into hello Catalog , Input in the terminal go install（ perhaps go install hello It works in any directory ）

Get into /bin Catalog , You'll notice that there's an extra name hello The file of , Input in the terminal hello

~$ hello
hello world!
Input hello Go language
~$ hello Go language
hello Go language
analysis
Now let's parse this program .

First of all to see package main

stay Go In language , All code must be subordinate to the package , every last Go Language programs must contain a main Bag and a main() function ,main() Function is the entry to the whole program , First executed . Actually ,Go Language may also contain init() function , Precede main() perform , Used to initialize packages . It should be noted that , There is no naming conflict between package name and function name .

Go The processing unit of the language is the package, not the file , stay Go The language compiler looks like , As long as the beginning of the package is the same , Then it belongs to the same package , It's like putting it all in one file , It's hard to understand, right ～～～ It's like sugar gourd , Although there are many Hawthorn in it , But every hawthorn is part of this sugar gourd . Because of this characteristic , We can split the package into any number of source code files .

import I don't need to introduce it

Go Language doesn't need ;（ Unless you enter multiple statements on the same line ）,if and for Statements don't need to be (), Semicolons are added automatically by the compiler .

Go The functions and methods of language are composed of func Keyword definition .

You may see := This weird expression , This expression does two things , Declaration and assignment , There is no need to declare that the variable type does not represent Go Language is a weakly typed language ,Go Language is a strong type of language , You don't need to declare a type because Go The type is derived from the initialization value .:= Can only be used in functions , If you declare package level variables , have access to var keyword ,var name = ？？？ perhaps var name type. And then there's who Why don't variables :=, Because once used who:="" This expression , It's equivalent to if A new statement named who The variable of , The life cycle is if Inside the statement , It's a local variable .

stay for In circulation , Used range keyword , Each loop returns keys and values , Values are stored in arg in , It's the key .,arg It's a strange expression , This is because Go Language does not allow you to declare variables without using , And we really don't need range Return key , So use _ This thing , It's like a garbage dump .

os.Args It's a string Type of slice （slice） and python almost

All right. , That's it -_-