Go is a modern generic purpose open source programming language that was officially announced at the end of 2009. It began as an internal Google project and has been inspired by many other programming languages including C, Pascal, Alef, and Oberon. Its spiritual fathers are Robert Griesemer, Ken Thomson, and Rob Pike, who designed Go as a language for professional programmers who want to build reliable and robust software. Apart from its syntax and standard functions, Go comes with a pretty rich standard library.

At the time of writing this book, the latest stable Go version is 1.8, which includes some handy new features including the following: feel free to skip this if you have not used Go before:

• New conversion rules exist that allow you to easily convert between types that are almost equal provided that some criteria are met. You can fix the import paths of the golang.org/x/net/name form to just the name of the Go source file using the go tool command without having to open the source files yourselves.
• The operation of the tool is stricter in some cases and looser in cases that used to generate false positives.
• There is now a default value for GOPATH Environment Variables when GOPATH is undefined. For Unix systems, the default value is $HOME/go.
• There are various improvements to the Go runtime that speed up Go.
• There is a sort.slice() function that allows you to sort a slice by providing a comparator callback instead of implementing sort.Interface.
• There is now a Shutdown method to http.Server.
• There exist various small changes to the database/sql package that give the developer more control over queries.
• You can create bugs using the go bug command.

You can easily find your version of Go using this command:

$ go version
go version go1.7.5 darwin/amd64  

The previous output is from a macOS machine hence the darwin string. A Linux machine would give the following kind of output:

$ go version
go version go1.3.3 linux/amd64

You will learn more about go tool, which you will use all the time, in the next chapters.

As I can imagine, you must be impatient to see some Go code; so here is the Go version of the famous Hello World program:

package main 
 
import "fmt" 
 
// This is a demonstrative comment! 
func main() { 
   fmt.Println("Hello World!") 
} 

If you are familiar with C or C++, you will find Go code pretty easy to understand. Each file that contains Go code begins with a package declaration followed by the needed import declarations. The package declaration shows the package that this file belongs to. Note that semicolons are not required for successfully terminating a Go statement unless you want to put two or more Go statements in the same line.

In Chapter 2, Writing Programs in Go, you will find out how to compile and execute Go code. For now, it is enough to remember that Go source files are stored using the .go file extension: your task is to choose a descriptive filename.