BeginnerCore syntax

Lab: Core syntax review

Consolidate your Go core syntax knowledge with quizzes covering all six lessons and coding challenges to try in your local editor.

Lab · optionalGoBeginner20 min

Recommended first

Structs and methods

By the end of this lesson you will be able to:

Recall key rules for variables, functions, control flow, collections, and structs
Predict Go compiler behaviour from short code snippets
Identify idiomatic Go patterns versus common mistakes

This is an optional lab. No new concepts — just a chance to consolidate what you've learned across the core syntax module. Work through the quiz sections, then try the coding challenges in your own editor.

Go's design philosophy is that the language should be easy to read, even by someone who didn't write it. This lab asks you to read short programs and predict what they do — or whether they compile at all. That habit of reading before running is one of the most efficient ways to internalise a language.

Section 1 — Variables and types

Knowledge check

1.
What is the zero value of a bool in Go?
nil0falseThere is no zero value — you must always initialise
2.
Does this code compile?
```
package main

var x := 10

func main() {}
```
Yes — := works at package scopeNo — := is only valid inside functionsYes, but only on Go 1.21+No — you cannot declare x without using it
3.
In Go, you can reassign a const after it has been declared.
TrueFalse

Section 2 — Functions

Knowledge check

Section 3 — Control flow

Knowledge check

1.
What does this print?
```
colors := []string{"red", "green", "blue"}
for i, c := range colors {
    fmt.Println(i, c)
}
```
red\ngreen\nblue0 red\n1 green\n2 blue1 red\n2 green\n3 blueCompile error — range returns only the element
2.
In a Go switch, what happens if no case matches and there is no default clause?
A runtime panicA compile errorNothing — execution continues after the switchThe first case executes as a fallback
3.
In if err := doWork(); err != nil { ... }, what is the scope of err?
The entire functionOnly the if block, not any else blockThe if block and any associated else/else-if blocksOnly the line where it is declared

Section 4 — Arrays, slices, and maps

Knowledge check

1.
What is wrong with this code?
```
s := []int{1, 2, 3}
append(s, 4)
fmt.Println(s)
```
Nothing — append modifies s in placeappend returns a new slice that is not captured; s still has 3 elementsThis panics because the slice is fullCompile error — append requires a pointer
2.
How do you check whether the key "x" exists in m map[string]int?
if m["x"] != nil { }if m.contains("x") { }v, ok := m["x"]; if ok { }if exists(m, "x") { }
3.
A sub-slice created with s[1:3] shares the underlying array with the original slice s.
TrueFalse

Section 5 — Structs and methods

Knowledge check

Coding challenges

These won't run in the browser — Go needs a local compiler. Use the project from the first lesson (go run main.go to execute).

Challenge 1: FizzBuzz

Write a fizzBuzz(n int) string function that returns "Fizz" if n is divisible by 3, "Buzz" if divisible by 5, "FizzBuzz" if both, and the string form of n otherwise. Use it in a loop from 1 to 20 and print the results. Use fmt.Sprintf("%d", n) to convert an integer to string.

Hint: Check the combined case (n%3 == 0 && n%5 == 0) first, otherwise "Fizz" or "Buzz" will match before you reach "FizzBuzz".

Challenge 2: Word count

Write a function wordCount(words []string) map[string]int that returns a map of each word to how many times it appears. Test it on []string{"go", "is", "fast", "go", "is", "simple", "go"}. Then range over the map and print each word with its count.

Challenge 3: Temperature converter

Define a Temperature struct with a Celsius float64 field. Add:

Fahrenheit() float64 — returns the Fahrenheit equivalent.
String() string — returns a human-readable string like "100.00°C / 212.00°F" using fmt.Sprintf.

Create a []Temperature slice with a few values and print each one.

Challenge 4: Stack (stretch)

Implement a stack using a struct wrapping a []int. Add methods Push(v int), Pop() (int, bool) (returns the top element and whether one was available), and Len() int. Use pointer receivers. Test by pushing several values and popping them — they should come out in reverse order.

When the agent's away

The best next step is writing small programs from scratch. Type every line — don't paste:

mkdir go-practice
cd go-practice
go mod init example.com/practice
# create main.go, write code, run it
go run main.go
go fmt ./...
go vet ./...

The official Go Tour at tour.golang.org is free, interactive, and covers everything in this module plus more. For deeper reading, the Effective Go document explains the idioms that distinguish good Go from merely correct Go.

Where to go next

You've completed the core syntax module. The natural next step is the intermediate track, which covers Go's interface system, goroutines and channels for concurrency, error wrapping, and standard library patterns for I/O and testing.

Finished reading? Mark it complete to track your progress.

Structs and methods

Define custom types with struct, access fields, and attach behaviour with value and pointer receivers — Go's approach to object-oriented design.

Interfaces

Go interfaces are satisfied implicitly — any type with the right methods qualifies, no declaration needed.

Lab: Core syntax review

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