What are the characteristics of golang package

Features: 1. The package name is generally lowercase, use a short and meaningful name; 2. The package name generally has the same name as the directory where it is located, or it can be a different name, and the package name cannot contain "-" and other special symbols; 3. Packages generally use domain names as directory names, which ensures the uniqueness of package names; 4. The package named main is the entry package of the application. If there is no main package when compiling the source code, it will not be compiled. Output executable files; 5. All source code files in a directory can only belong to the same package, and source code files that also belong to the same package cannot be placed in multiple directories.

The operating environment of this tutorial: Windows 7 system, GO version 1.18, Dell G3 computer.

The Go language uses packages to organize source code. A package is a collection of multiple Go source codes and is an advanced code reuse solution. Go language provides us with many built-in packages, such as fmt, os, io, etc.

Any source code file must belong to a certain package, and the first line of valid code in the source code file must be the package pacakgeName statement, through which the package you are in is declared.

Basic concepts of packages

Go language packages use the organization form of a directory tree. Generally, the name of a package is the directory where its source file is located. Although the Go language does not mandate that the package name must have the same name as the directory name where it is located, it is still recommended that the package name have the same name as the directory where it is located, so that the structure is clearer.

Packages can be defined in very deep directories. The definition of the package name does not include the directory path, but the full path is generally used when referencing the package. For example, define a package c under GOPATH/src/a/b/. In the source code of package c, you only need to declare it as package c instead of package a/b/c. However, when importing the c package, you need to bring the path, such as import "a/b/c".

Go language package features

• Package names are generally lowercase, use a short and meaningful name;

• The package name generally has the same name as the directory where it is located, or it can have a different name from the directory (but it is best not to do this). The package name cannot contain special symbols such as -.

• Packages generally use the domain name as the directory name, which ensures the uniqueness of the package name. For example, the packages of GitHub projects are generally placed in GOPATH/src/github.com/userName /projectName directory.

• The package named main is the entry package of the application. When compiling the source code file that does not contain the main package, you will not get an executable file.

• All source code files in a folder can only belong to the same package. Source code files that also belong to the same package cannot be placed in multiple folders.

Go language package design ideas

The purpose of any package system design is to simplify the design and development of large programs Maintenance work, by putting a set of related features into an independent unit for easy understanding and updating, while maintaining relative independence from other units in the program while updating each unit. This modular feature allows each package to be shared and reused by other different projects, and can be distributed and reused uniformly within the project or even globally.

Each package generally defines a different namespace for access to each identifier within it. Each namespace is associated with a specific package. Let's choose short and concise names for types, functions, etc., so as to avoid name conflicts with other parts when we use them.

When we modify a source file, we must recompile the package corresponding to the source file and all other packages that depend on the package. Even when built from scratch, the Go language compiler compiles significantly faster than other compiled languages. The lightning-fast compilation speed of Go language is mainly due to three language features.

Explicit declaration

All imported packages must be explicitly declared at the beginning of each file, so that the compiler does not have to read and analyze the entire source file to determine package dependencies.

Prohibit circular dependencies

Prohibit circular dependencies of packages. Because there are no circular dependencies, the dependencies of packages form a directed acyclic graph. Each package can be Compile independently, and most likely be compiled concurrently.

Target file

The target file of the compiled package not only records the export information of the package itself, the target file also records the dependencies of the package. Therefore, when compiling a package, the compiler only needs to read the object files of each directly imported package, without traversing all dependent files.

【Related recommendations: Go video tutorial, Programming teaching】

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