Before we start to learn. The basic composition of Package declaration Introduction packet Function Variable Statement Annotation Next let’s take a look at the simple code that outputs “Hello World!”: Let’s take a look at the various parts of the above program: The first line of code Next line Next line Next line Next line When identifiers (including constants, variables, types, function names, structure fields, and so on) begin with an uppercase letter, such as: Let’s take a look at how to write Open the editor as shown in Save the above code as Open the command line and go to the directory where the program file is saved. Enter a command If you operate correctly, you will see “Hello World!” on the screen. The output of words. We can also use It is important to note that
Go
before building the basic module of the programming language, let’s take a look at
Go
structure of the simplestprogram in a language. 2.3.1. Go Hello World instance #
Go
language consists of the following parts:
&
Expression.Example #
package main
import "fmt"
func main() {
/* This is my first simple program */
fmt.Println("Hello, World!")
}
package
main
package name is defined. You must indicate which package the file belongs to in the first uncommented line of the source file, such as
package
main
.
package
main
Represents a program that can be executed independently, each
Go
applications contain a file named
main
donovan’s bag.
import
"fmt"
tell
Go
compiler this program needs to use the
fmt
package (function of, or other element of)
fmt
, the package implements the function to format IO (input/output).
func
main()
is the function that the program begins to execute.
main
functions must be included in every executable program, and are generally the first to execute after startup (if any
init()
function executes the function first.
/*...*/
is a comment and will be ignored when the program is executed. Single-line comments are the most common form of comments, and youcan use them anywhere with
//
the single-line comment at the beginning. Multiline comments, also known as block comments, have been marked with
/*
start with a
*/
at the end, and cannot be used in nesting, multiline comments are generally used for the documentation description of the package or code snippets that are commented into blocks.
fmt.Println(...)
you can output the string to the console andauto matically add newline characters at the end
\\n
. Use
fmt.Print("hello,
world\n")
the same results can be obtained.
Print
and
Println
, these two functions also support the use of variables, such as
fmt.Println
(arr)
. If not specified, they will set the variables in the default print format
arr
output to the console.
Group1
an object that uses this form of identifier can then be used by the code of the external package (the client program needs to import the package first), which is called an export (like in object-oriented languages
public
identifiers are not visible outside the package if they begin with lowercase letters, but they are visible and available inside the entire package (like in object-oriented languages
protected
). 2.3.2. Execution
Go
program #
Go
code and execute it. The steps areas follows:
Sublime2
to add the above code to the editor.
hello.go
go
run
hello.go
and press enter to execute the code.$ go run hello.go
Hello, World!
go
build
command to generate binaries:$ go build hello.go
$ ls
hello hello.go
$ ./hello
Hello, World!
2.3.3. Be careful #
{
you cannot put it on a separate line, so the following code generates an error at run time:Example #
package main
import "fmt"
func main()
{ // Error, {cannot be on a separate line
fmt.Println("Hello, World!")
}