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Install Go
The Lantern control room has gone silent at 02:17.
Set up Go, create a module, run go test, and read a failing test...✓
◈ GREYHAVEN / INVESTIGATION ROUTE
Case files.
Choose an act on the map. Its Go chapters and story cases appear below.
39 CASES / 06 ACTS
ACT 01CASES 01-08
The Missing Minutes
Recover the first packets and learn why the dashboard cannot be trusted.
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Hello, World
A terminal on the dark relay keeps printing an unfinished greeting.
Write functions with parameters and return values↗
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Integers
North Sluice's packet carries two counters: one for alerts created, one for alerts delivered.
Use integer arithmetic, function signatures, and clear test cases...·
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Iteration
A weak beacon repeats the same fragment until another station acknowledges it.
Use for loops, repeated operations, and a benchmark to compare a...·
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Arrays and slices
The maintenance channel contains packet fragments from several towers.
Use arrays, slices, len, range, variadic arguments, and test coverage·
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Structs, methods & interfaces
Imani lays out three kinds of record: a sensor reading, a human notice, and a relay receipt.
Model domain values with structs and methods·
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Pointers & errors
Ro reaches the North Sluice cabinet and tries a remote calibration.
Use pointers for shared state·
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Maps
The seven absent alerts were addressed to station codes, while Greyhaven's map uses neighborhood names.
Store and look up values by key·
ACT 02CASES 09-15
The False All-Clear
Compare independent sources as the storm and the code grow less predictable.
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Dependency Injection
Asha needs a copy of the warning draft, but the production transmitter is still suspect.
Pass dependencies through interfaces or functions·
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Mocking
The port relay claims it forwarded every message.
Use test doubles to observe interactions·
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Concurrency
Ro has minutes before the access road floods.
Use goroutines and channels to collect independent results·
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Select
A live sensor and a backup radio now offer conflicting gate positions.
Use select to receive from competing channels and respond to timeouts·
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Reflection
Imani finds an unlabelled envelope in an older archive.
Inspect struct fields and tags with reflection·
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Sync
Parallel searches return contradictory versions of the same event.
Protect shared data with a mutex and coordinate workers with WaitGroup·
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Context
The search for the override's author fans out across slow archives.
Propagate cancellation and deadlines through a request·
ACT 03CASES 16-21
The Buried Order
Reconstruct the override, its author, and the true state of the sluice.
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Intro to property based tests
Halden's authorization record refers to an old storm protocol by a Roman-numeral revision.
Use a conversion kata to explore invariants, round trips, and...·
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Maths
Ro radios that the gate's mechanical dial is partly visible through spray, but its photograph is skewed.
Use the math package and geometry to produce a visual clock or...·
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Reading files
The port office sends a local archive on removable storage.
Read files, parse records, and test behavior with representative data·
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Templating
Asha prepares an internal incident brief.
Render data safely with html/template and use approval-style tests...·
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Generics
Three archives use different record types but the same chronological search pattern.
Write a generic data structure or function while keeping types and...·
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Revisiting arrays and slices with generics
The timeline is complete, but Asha still needs one concise answer: which districts received a valid warning, and which did not?
Use generic collection helpers such as Reduce to summarize a slice·
ACT 04CASES 22-25
Proof Under Pressure
Test the warning path before anyone relies on it.
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Introduction to acceptance tests
The team's repaired logic passes its unit tests, yet the old Lantern still loses a warning when several parts run together.
Test observable system behavior across component boundaries,...·
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Scaling acceptance tests
One successful district is insufficient.
Organize larger acceptance suites with reusable fixtures and clear...·
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Working without mocks
A mocked transmitter says the dispatch code called Send, but that does not prove a receiver could read the message.
Use fakes and contracts where they make integration behavior more...·
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Refactoring Checklist
The emergency code works, but it contains duplicated routing decisions and a special case added during the night.
Refactor with a passing test suite, small steps, and explicit...·
ACT 05CASES 26-33
The Public Signal
Build a reliable public warning service for Greyhaven.
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Build an application: the public signal
Asha approves a temporary public alert ledger.
Turn tested functions into an application with an explicit user...·
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HTTP server
The new ledger needs a reachable address.
Create and test HTTP handlers with net/http and httptest·
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JSON, routing and embedding
The plain status page is readable, but district devices need structured data and a stable route.
Return JSON, route requests, and embed static assets in a Go...·
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IO and sorting
Warnings arrive from several sources.
Persist records through I/O boundaries and sort them for a...·
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Command line & package structure
Asha needs the public server running while Imani imports another archive.
Separate command-line entry points and packages·
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Time
The tide forecast moves forward.
Use time for scheduling, deadlines, and testable time-dependent...·
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Revisiting time with testing/synctest
The new escalation logic passes when run alone and fails occasionally in the full suite.
Test real timer-driven code with testing/synctest without slow or...·
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WebSockets
The gate's physical status changes as Ro works the manual release.
Build and test a live bidirectional connection for timely status...·
ACT 06CASES 34-39
The Inquiry
Preserve evidence and make the system safer for the next storm.
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OS Exec
After the storm, an inquiry asks Imani to decode a proprietary recorder file.
Separate an external command from data processing so the latter...·
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Error types
The inquiry discovers that several old dashboard errors were all displayed as “unavailable.” Operators could not tell a...
Represent meaningful failure categories with custom error types...·
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Context-aware Reader
An archive reader can hang while fetching a damaged remote file.
Carry cancellation into slow reads and handle partial work safely·
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Revisiting HTTP Handlers
Residents continue using the public ledger after the emergency.
Separate handler responsibilities and compose HTTP behavior so...·
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Why unit tests and how to make them work for you
At the inquiry, Asha is asked why her team trusted a new service built during a storm.
Use tests as executable examples and feedback for design, not just...·
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Anti-patterns
Greyhaven keeps the ledger, and a new maintenance team inherits its tests.
Recognize brittle tests, excessive mocking, unclear abstractions,...·