Tag golang

Testing with Go

An integral part of the development licefycle is writing tests. Write tests early, write tests often as they say. Go makes it very easy to write tests. The following post will go through the basics of testing with Go. Let’s say we have a program that counts the number of vowels, consonants, digits and everything else within an input string. It may look something like this: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 package main import ( "flag" "fmt" ) // CountChars counts the number of characters in a string func CountChars(str string) (int, int, int, int) { vcount := 0 ccount := 0 dcount := 0 ocount := 0 for i := 0; i < len(str); i++ { switch str[i] { case 'a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U': vcount++ case 'b', 'c', 'd', 'f', 'g', 'h', 'j', 'k', 'l', 'm', 'n', 'p', 'q', 'r', 's', 't', 'v', 'w', 'x', 'y', 'z', 'B', 'C', 'D', 'F', 'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'V', 'W', 'X', 'Y', 'Z': ccount++ case '1', '2', '3', '4', '5', '6', '7', '8', '9', '0': dcount++ default: ocount++ } } return vcount, ccount, dcount, ocount } func main() { inputStr := flag.

Introduction to Go Modules

Table of Contents Preface Why Go Modules Philosophy Example Preface All the content for this post was gathered by reading the 7 part blog series by Russ Cox and other notes. There is also an introductory post on the Go blog. I would encourange you to read them as well. Why Go Modules Before jumping into the workings of Go modules, we should first understand why we need it in the first place.

Defer on exit

Working with go, sometimes you may want to run a deferred action on Exit. Something like: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 package main import ( "fmt" "os" ) func main() { // THIS WILL NOT WORK defer fmt.Println("World") fmt.Println("Hello") // some code here... os.Exit(0) } In the above code, World will never get printed. This is because defer is not run on os.

Populating go vars at build time

When we build go executables, one common command is the version command. It should tell you the commit, version number etc of the released executable. However, we don’t want to hardcode these in code. We want to populate these variables at build time. Here is a common pattern that will let you do this. Let’s assume you have a main.go that imports a package version and prints out the output of version.

Init function in modules

A Go package can have an init function. This function is called at the time when the package is imported. You can put in any initialization you want here. e.g. 1 2 3 4 5 6 7 8 9 10 11 12 13 package main func init() { fmt.Print("Hello") } func init() { fmt.Print(" World") } func main() { fmt.Println(" People") } The above will print out Hello World People.