002-First-Program

First Go Program & Basics

BUILDING & RUNNING GO PROGRAMS:

• Build a Go program:

  • While inside a program directory, type:
    • go build

• Run a Go program:

  • While inside a program directory, type:
    • go run main.go

WHAT IS $GOPATH?

• $GOPATH is an environment variable which points to a directory where the downloaded and your own Go files are stored.

  • On Windows, it's in: %USERPROFILE%\go

  • On OS X & Linux, it's in: ~/go

  • NOTE: Never set your GOPATH manually. It's by default under your users directory.

• GOPATH has 3 directories:

  • src: Contains the source files for your own or other downloaded packages. You can build and run programs while in a program directory under this directory.

  • pkg: Contains compiled package files. Go uses this to make the builds (compilation & linking) faster.

  • bin: Contains compiled and executable Go programs. When you call go install on a program directory, Go will put the executable under this folder.

    • You might want to add this to your PATH environment variable if it's not there already.

WHERE YOU SHOULD PUT YOUR SOURCE FILES?

• $GOPATH/src/github.com/yourUsername/programDirectory

• Example:

  • My GitHub username is: aditya43

  • So, I put all my programs under: ~/go/src/github.com/aditya43/

  • And, let's say that I've a program named hello, then I put it under this directory: ~/go/src/github.com/aditya43/hello

FIRST PROGRAM

• Create directories:

  • OS X & Linux (or git bash):

    • Create a new directory:
      • mkdir -p ~/go/src/yourname/hello
    • Go to that directory:
      • cd ~/go/src/yourname/hello

  • Windows:

    • Create a new directory:
      • mkdir c:\Go\src\yourname\hello
    • Go to that directory:
      • cd c:\Go\src\yourname\hello

• Create a new code main.go file under Visual Studio Code.

• And add the following code to it and save it.

• Then, return back to the command-line.

  • Run it like this: go run main.go

package main

import "fmt"

func main() {
    fmt.Println("Hello Aditya.")
}

NOTE:

• There is a new Go Modules support that allows you to run your programs in any directory that you want.