Golang Beginner Tutorial Series - Writing Hello World by Hand

create a file and write nothing. try compiling as followsprogram1.go

cmd-prompt> go run program1.go

an error similar to the following will be printed:

package :
program1.go:1:1: expected 'package', found 'EOF'

in a language, all files must belong to a package. currently, you only need to understand that you can declare one at the head of the file, where it is a keyword, a package name for yourself.
in large programs, packages can be well organized for various functions.
for example, if you want to write a virtual model of a vehicle, you should put all the models that belong into a package called a package, and put all the models that belong into the package.
organization-related features are just one use for packages, and more will be covered in a follow-up article.Gopackage namepackagenamecarcarsbusbuses

now let’s add a statement to the file we just created and then re-execute the command

program1.go content

package main

after executing the previous command, the following error is printed:

runtime.main: undefined: main.main

Gowhen the program starts, it needs to have an identifiable entry in the file. just as a car must have a key to start the ignition, a computer needs to have a power-on button, and a program needs to have a function.Gomain

add another line to the file and try again

program1.go content

package main

func main() {}

execute the commandgo run program1.go

the program executed correctly, but since we didn’t do anything else, the program exited quickly.

congratulations, so far we have created our first program. although it is not useful, it can already work normally.

let’s go ahead and add a line

program1.go content

package main

func main() {
 Println("Hello world")
}

if you try to run, you will print the following error

program1.go:4: undefined: Println

Printlnis an input to the screen. After executing the command, the compiler reports that it is not defined. Why? Remember the packages mentioned earlier? Yeah, here we need to use the bag. Functions like this are stored in some packages. However, currently these packages are not actively introduced due to us, but can not use drops. If we need to use the features in these packages, we need them first. It’s like when we buy a car from overseas. Ok, let’s try.Printlnimportimport

The function Println and other functions that read and write text and characters are stored in an abbreviation called a packagefmtformatting

The Go programming language follows a short and concise manner. If you write Java code, you define it in a long naming style. For example, the above will be very normal to be called. But in the Go language, it is necessary to break this routine and pursue simplicity. At first, I didn’t get used to this pattern, but after using it for a while, Zhen nyima was amazing. The code has become cleaner, it’s faster to read, and oddly enough, it’s not reduced in readability. Personal opinion Oh ~~~formatting packageformatting

so far, let’s add a few lines of code

package main

import "fmt"

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

run the program with the following output:go run program1.go

Hello world

Wow, isn’t it amazing, we just added a statement below and the first Go program is already working. After that, it can be called by way. Got it, it’s that simple.packageimportimportPrintln包名.