03-learning-golang-2025-08-31

References

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Introduction

Some random notes I took when following the basic golang tutorial from Boot.dev

Here is a basic “Hello World” program in Go,

package main
 
import "fmt"
 
func main() {
    fmt.Println("Hello World")
}

Going to skip mentioning the package and import moving forward - unless it’s something new. Here is how to declare variables,

func main() {
    // variable initialization
    var smsSendingLimit int
    var costPerSMS float64
    var hasPermission bool
    var username string
    
    fmt.Printf("%v %.2f %v %q\n", smsSendingLimit, costPerSMS, hasPermission, username)
}

The output of the above looks like this,

0 0.00 false ""

I find the %v working for both int and bool weird. Like - if we’re going to reuse characters, why not the same for all? And why %q for strings? That’s new. Why not the usual %s ?

The earlier seems to be the “sad” way of declaring variables. The better approach seems to be this,

mySkillIssues := 42

The walrus operator declares the variable and assigns it a value at the same time. The language uses type inference to puzzle it out.

Oh. When the println() method is called like this,

fmt.println(messageStart, age, messageEnd)

in the output, a space is automatically inserted between the characters. That’s convenient!

Got some explanations about the boilerplate.

package main → lets the compiler know that we want the code to compile and run as a standalone application. The alternative is that we might have been building a library.

import "fmt" → imports fmt from the standard library.

func main() → defines the entrypoint.

Here is an interest website/dictionary; https://techterms.com/definition/truncate

In Go, when we convert between types - float to int specifically, we lose data. The variable is not rounded - it is truncated.

Hmm… now that I think about it, I don’t feel I’ve actually done that kind of conversion in any of my day jobs. 🤔

Here is a list of default go types,

bool
string
int
uint
byte
rune
float64
complex128

What the heck is a rune type? A bit of searching tells me that it is a unicode codepoint. Usually it is equivalent to int32.

Constants are declared using the const keyword.

Finally got an answer. The %v that is used in fmt.Printf() is a default. It can be used for any variable.

fmt.Printf() will print a formatted string to STDOUT and fmt.Sprintf() will return the formatted string (it does not do any printing directly)

Here is a new way of using the import keyword,

import (
    "fmt"
    "unicode/utf8"
)

random website = https://emojipedia.org/bear

To measure unicode characters in Go, we need to use this,

const name = "🐻"
utf8.RuneCountInString(name)

above will return 1. But if you use len(name), it will return 4.

Just finished the variables section. That was a lot more than I was expecting!