Practice Go online: 10 exercises and a playground

In order, each one introducing a single new idea. Press Run to check your answer; hints open one at a time.

1. 1Library Due-Date ReminderDeclaring variables with := and printing them with fmt.Println and fmt.Printf, including a format string that must end with \n
2. 2Recipe ScalerArithmetic on ints with +, -, *, and /, including that integer division truncates instead of rounding (7 / 2 is 3)
3. 3Parking Meter StatusBranching with if / else if / else and comparison operators (<=, etc.)
4. 4Bus TimetableCounting for loops (for i := 0; i < n; i++) that compute a new value on each pass
5. 5Poem Word CounterReading a line with bufio, cleaning it with strings.TrimSpace, and splitting it into words with strings.Fields
6. 6Tool Shed InventorySlices: literals, growing one with append (and keeping its result), indexing, and len() inside a loop
7. 7Currency ConverterMaps: map[string]float64 literals, looking values up by key (including the zero-value gotcha for a missing key), and formatting floats with %.2f
8. 8Board Game LeaderboardWriting and calling a function with a parameter and a return value: func highestScore(scores []int) int
9. 9Playlist RuntimeDefining a struct with fields and a method on it (func (s Song) Format() string), used across a slice of structs
10. 10Tip Jar SplitCombining a struct, a helper function, and a loop to compute a proportional split with float formatting (%.1f and %.2f)

Questions people ask

Is this the real Go compiler?

It is a real Go interpreter (yaegi) rather than the compiler you would run locally, so it understands genuine Go syntax and the standard library and reports real errors like an unused import — the trade-off is that it interprets rather than compiles to a native binary, and third-party packages are not available.

Can I read input with bufio and os.Stdin?

Yes. Lines typed into the input box beside the editor are what os.Stdin provides, so bufio.NewReader(os.Stdin) reads them exactly as it would on your own machine.

Do I need go.mod or any setup?

No. Every exercise is a single package main file with its own func main, pasted straight into the editor — there is no module system here, just the language and its standard library.

What is here besides the exercises?

The 10 exercises come first, and a blank playground is there for trying anything else you want to build with Go's standard library.