KHOI | Blog

Learning Go — Week 4

Mon, Jan 08, 2024 · 4 min read
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Table of contents

Error handling

I love how Go does error-handling!

Error handling is not done via exceptions in Go. Instead, errors are normal values of types that implement the built-in error interface. The error interface is very minimal. It contains only one method Error() that returns the error message as a string. — Exercism

Super minimal!

However, this gives you the responsibility to be specific about your error message.

I didn’t know that by convention, the error message starts with a lowercase letter and not end with a period.

Since most functions in Go include an error as one of the return values, you will see/use the if err != nil pattern all over the place in Go code.

You can use a struct to create a custom error type, as shown below:

type MyCustomError struct {
  message string
  details string

func (e *MyCustomError) Error() string {
  return fmt.Sprintf("%s, details: %s", e.message, e.details)

func someFunction() error {
  // ...
  return &MyCustomError{
    message: "...",
    details: "...",

Besides this, I also learned about Go’s regexp.

Zero values

Go does not have a concept of empty, null, or undefined for variable values. Variables declared without an explicit initial value default to the zero value for their respective type.

Type Zero Value
boolean false
numeric 0
string “”
pointer nil
function nil
interface nil
slice nil
channel nil
map nil

First class functions

This is the last concept on Exercism that I need to learn.

Functions are first-class values. This means that you can do with functions the same things you can do with all other values - assign functions to variables, pass them as arguments to other functions or even return functions from other functions.

For instance:

import "fmt"

func engGreeting(name string) string {
	return fmt.Sprintf("Hello %s, nice to meet you!", name)

// greeting is a variable of type func(string) string
greeting := engGreeting

func dialog(name string, greetingFunc func(string) string) {
	fmt.Println("I'm a dialog bot.")
dialog("Alice", greeting)