Packages

Example

https://yingshaoxo.blogspot.com/2021/06/how-to-create-package-with-golang.html

go env -w  GOPROXY=https://goproxy.io

Like Python, sometimes, you want to separate your codes to different files.

So it can be organized.

In Python, you use import to load function from .py file.

In Golang, you will also use import to load function from .go file.

But Golang file structure is different.

For example，a tree of a project may look like this:

src
├── hi
│   └── a_go_file.go
└── main.go

//a_go_file.go
package hi

import "fmt"

func init() {
    fmt.Println("You are runing init() function from hi package")
}

func Say_hello() {
    fmt.Println("You are runing Say_hello() function from hi package")
}

//main.go
package main

import (
    "./hi"
    "fmt"
)

func main() {
    fmt.Println("You are runing main() function from main package.")
    hi.Say_hello()
}

If you run main.go，you'll get:

You are runing init() function from hi package
You are runing main() function from main package.
You are runing Say_hello() function from hi package

That tells us some facts:

1. golang package was separated by folder. In that folder, all your .go file must declare the package name by package *

2. you can import your own packages from main.go with ./your_package_name

3. before golang import any package, it will run the init() function first

4. if you want to export or use a function from a package, the first character of that function name must keep capitalizing.

Sometimes, people would like to put all their source codes to ~/go/src

In that case you will import a package using github.com/yourname/projectname

It's good to do with if you don't want to handle the folder-file structure with relative import

And by doing so, vim YouCompleteMe could be able to work correctly

By the way, in case you don't know: use `go get ./...` to install all missing packages for a Go project.