Go Practice
Learn how to write Go programs step by step, one module at a time, with each module building on the last.
Go 1.26Data & Decisions
Learn the building blocks of Go: working with numbers and text, making decisions with if, for and switch, and organising data in slices and maps.
Server Bills
Bill servers by the hour in whole numbers: round part-hours up, convert to int64 before multiplying so the yearly forecast never overflows, and format cents as a euro label with fmt.Sprintf.
Health Checks
Sort each uptime check into up, slow or down with a switch, find the first server down and the longest outage in a for loop, and double the retry delays up to a limit.
Server Fleet
Count servers per region with a map, list the regions in sorted order with maps.Keys and slices.Sorted, and copy the online servers into a new slice without changing the one you are given.
Status Page
Turn a day of health checks into a status page: classify each check, group the checks by region in a map, and show each region's availability in sorted order, as a percentage that never rounds up.
Types & Errors
Learn how to design your own types in Go and handle errors: structs with methods, interfaces for things that behave alike, and errors that carry their cause.
Servers
Model a server as a struct whose pointer-receiver methods start, stop and resize it, refuse bad input with an error from its constructor, and stop a whole slice of servers in place.
Alert Channels
Send one alert through email, chat and pager behind a single interface, print severities by name with a String method, and use a type assertion so that only critical alerts reach the pager.
Deploy Errors
Wrap a not-found error with %w, return a custom quota error or a real nil, and explain any deploy failure by looking through the wrapping with errors.Is and errors.AsType.
Deploy Desk
Replay a day of deploy requests: deploy each release that fits the cluster, report every failure with its step number through an interface, and count the failures by cause with errors.Is and errors.AsType.
Generics & Iterators
Learn how to write reusable code in Go: functions and types that work for many types, and iterators that process data one item at a time.
Metric Helpers
Write generic helpers for the company's metrics: find the largest value with cmp.Ordered, clamp a value into a range, and add up and average any number type, named types like Millis included, with a Number constraint.
Metric Window
Build a generic Window[T] that keeps the last N values, drops the oldest when full, hands out a copy of its items, and finds its largest value with a function constrained by cmp.Ordered.
Log Streams
Read a log one line at a time with iterators: split text into lines with strings.Lines, keep only ERROR lines, number them from 1, and take the first N without reading further.
Metrics Report
Turn a day of request logs into a metrics report: parse each line through an iterator, average the response times with a generic function, and keep the most recent ones in a generic window.
Frequently asked questions
4What will I practice in this path?
3 modules: Data & Decisions, Types & Errors and Generics & Iterators.
How many challenges are there, and how hard are they?
12 challenges, all easy.
What does this path run on?
Challenges run on Go 1.26.
Do I need to install anything?
No. Every challenge runs in a browser-based IDE with everything already set up, and your code is graded automatically against a test suite.