如何在go中编写包？

Question

go is my first statically typed and compiled language so I am not sure about how to go about doing some things like writing packages...Should I write a package like...

package mypkg

import "fmt"

func mypkg {
    fmt.Println("mypackage")
}

and then import this into the main package....install it and then test if it works?

Or should I write mypkg like this...

package main

import "fmt"

func mypkg() {
    fmt.Println("mypackage")
}

func main() {
    mypkg()
}

Should I do it this way to make sure that I can call go run mypkg and see if it works, then delete the main function and rename the package and then work on the rest of the library?

Or did I miss the point entirely and I should do something else?

Answer 1

Here are some basic steps to get you going if you want to use packages.

Create a folder called mypkg in the folder you're working in. In that folder create a mypkg.go file with the following code (note the capital letter in the function name. You need to do this so main.go can see it).

package mypkg

import "fmt"

func Mypkg {
    fmt.Println("mypackage")
}

Now install the package just by typing go install while you're still in your mypkg directory. This will create a linkable object file you can use.

Now go back to your starting directory and create main.go with the following code:

package main

import (
     "...(path to your mypkg folder)/mypkg"
     "fmt"
)

func main() {
    mypkg.Mypkg()
    //optional
    //fmt.Println("whatever")
}

Now run it by typing go run main.go. This will compile and run main.go that uses the previous mypkg package you created.