Learning Go programming

Useful links

• Presentation
• Language specification
• Package documentation
• Package source code

Install environment

Install Go

https://golang.org/doc/install

Add go/bin directory to you PATH in $HOME/.profile. Test your installation:

$ go version
$ go env

Check in go env the GOPATH if you don't like it you can change it.

The main workspace is going to be a different one, the GOPATH will store the downloaded libraries.

Go tool is the swiss army knife. Check out what it can do:

$ go help

Install an IDE

Visual Studio Code

Download

(A short tour)[https://rominirani.com/setup-go-development-environment-with-visual-studio-code-7ea5d643a51a]

Check that gopath is correct: ctrl+` (open terminal) and check go env

Add go extension

• ctrl(mod)+shift+x (open extensions)
• filter: go lang
• Install rich go language support
• Whenever it asks for installing plugin install.
• add folder to workspace course/
• debug hello/main.go

ctrl-space completion for fmt.Println

GoLand

• no need to subscribe, that's only for email updates.
• Download, run goland/bin/goland.sh
• When you get username/password click on evaulate
• Open project, course/
• Check that you can debug hello.go
• Checkand that you get code completion.

Let's create the working directory for the codelabs

Choose a working directory where you want to do the codelabs and remember it. It should be outside of the $GOPATH.

$ mkdir gocourse
$ cd gocourse
$ go mod init mycompany.com/gocourse
$ go list -m ...

If you like git, create a git repository now:

$ git init

Add Hello World program:

# In gocourse directory.
$ mkdir hello
$ cd hello
$ touch hello.go

Edit hello.go:

package main

import "fmt"

func main() {
	fmt.Println("hello world!")
}

$ go run hello.go
$ go build hello.go
$ ./hello
$ go help build

You can also run by specifying the whole package name:

$ go run mycompany.com/gocourse/hello

Read documentation from console.

$ go doc fmt
$ go doc fmt.Println

get the training repository

The training repository contains the codelabs.

$ cat go.mod
$ go run github.com/acsaba22/go/hellocourse
$ cat go.mod

# Notice that a new package was added

$ go list -m ...

Check where the dependency was added in your $GOPATH.

$ go list -m -f '{{.Dir}}' ...acsaba22/go
# Go to that directory, perhaps in a second terminal:
$ cd `go list -m -f '{{.Dir}}' ...acsaba22/go`
$ ls
$ cd hellocourse
$ cat main.go
$ go run main.go

Use a library

Go back to your workspace and read the documentation on how to use a function from the training repository:

$ cd ~/gocourse
$ go doc github.com/acsaba22/go/hellolib
$ go doc github.com/acsaba22/go/hellolib.Greeting

Change hello/hello.go to call the Greeting function and print the result. Then run again:

$ go run hello/hello.go

Check the sourcecode of hellolib/greetings.go, it contains the actualGreeting function.

Try using hellolib.actualGreeting.

$ go run hello/hello.go
# command-line-arguments
hello/hello.go:12:14: cannot refer to unexported name hellolib.actualGreeting