golang package usage

Go language is an advanced programming language developed by Google. It is characterized by simplicity, efficiency, speed and high security. Golang is a language that supports multi-threading and coroutines, and supports high concurrency. It is a popular language now. In the use of Go language, package is a very important concept. Below we will introduce the usage of golang package in detail.

1. The concept of package

Package refers to a group of related functions, types, variables and other code combinations. In the Go language, each file must declare the package to which it belongs, which is the package name. Packages can be referenced by other programs to achieve code reusability and maintainability. Each package has a name and needs to be introduced through the import statement when using it.

2. How to introduce a package

In Go language, use the import statement to reference a package. The specific format is as follows:

import "package name"

Or use the following syntax structure:

import (

<code>   "包名1"
   "包名2"</code>

)

When introducing a single package, you can directly use the package name to access functions and other contents, for example ：

import "fmt"

func main() {

<code>   fmt.Println("hello world")</code>

}

When introducing multiple packages, use the package name as a prefix, for example:

import (

<code>   "fmt"
   "time"</code>

)

func main() {

<code>   fmt.Println("Hello world")
   time.Sleep(time.Second)</code>

}

3. Package access

In the Go language, all functions, variables and structures of the package can be accessed, which means that programmers need to understand all the contents of the package to fully utilize and master the package.

In the Go language, some functions and variables must be exported, which means the first letter must be capitalized, for example:

package main

import "fmt"

func SayHello(name string) {

<code>   fmt.Println("Hello,", name)</code>

}

In exported functions, variables and structures, all identifiers starting with uppercase letters are exportable. Otherwise, they are not exportable. For example:

package mymath

func Add(a, b int) int {

<code>   return a + b</code>

}

func sub(a, b int) int {

<code>   return a - b</code>

}

In the above example, Add is an exportable function and sub is a non-exportable function.

4. Package Management

In the Go language, package management is very convenient and can be managed in the following ways:

1. Official Standard Library

The official standard library of Go language is very comprehensive and includes many commonly used functions and tools. You can choose to use them during the development process without reinventing the wheel.

2. Third-party library management

There are many third-party libraries, which can be installed and managed using the go get command, for example:

go get -u package Name

Among them, the u option indicates that go get will update existing packages in the local code base.

3. Source code installation package management

If necessary, we can also manage it through source code installation packages to gain more control.

5. Package development

In the Go language, any file must declare its package name. Developing a new package mainly includes the following steps:

1. Define the package name

In the first line of any go source file, you must declare which package it belongs to:

package package name

2. Define export variables or functions

Define a function or variable that can be exported and used with other packages:

func MyFunction() {

<code>   //</code>

}

var MyStr string

Such functions and variables can be imported and used in other packages.

3. Define private variables and functions

Define some private variables and functions that cannot be imported and used by other packages, that is, the first letter of the name is lowercase:

func myFunction() {

<code>   //</code>

}

4. Related function implementation

Define the source code for implementing related functions.

6. Conclusion

In the Go language, packages are a very important concept, which greatly improves the reusability and maintainability of the code. In addition, package management and development are also knowledge points that programmers must understand and master. Through the introduction of this article, I believe readers can already master the usage of golang package.

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