テーマ： go
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Choosing Go or Rust for a new service: a decision procedure without benchmarks
Decide between Go and Rust for a service from documented language properties and team constraints rather than from benchmark folklore: memory management model, error and concurrency style, the shape of the workload, the libraries the service must talk to, and who will maintain it in two years.
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Cancellation and deadlines in Go with context.Context
Thread a context.Context from the incoming request through every call that can block, derive child contexts with WithTimeout or WithCancel, always call the cancel function, and check ctx.Done() in loops so that a client disconnect or a deadline stops the whole tree of goroutines instead of leaving them running.
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Go elapsed time: serialization loses the monotonic clock component
Keep local duration measurement separate from persisted timestamps and cross-process deadline policies.
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Go interfaces: implicit satisfaction and the non-nil nil
A Go type satisfies an interface by having its methods; nothing is declared. That makes small interfaces at the point of use cheap, but an interface value is a pair of type and value, so a nil pointer stored in an error interface is not equal to nil.
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Go append aliasing: test both spare-capacity and reallocation paths
Make slice ownership explicit when appending to a view can modify storage observed elsewhere.
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Go error handling: wrapping with %w, errors.Is and errors.As
Go functions return errors as ordinary values; add context with fmt.Errorf and the %w verb so the original stays reachable, then test the chain with errors.Is for sentinel values and errors.As (or the generic errors.AsType) for types, instead of comparing strings or using ==.
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Goroutines, channels and the sync package: Go concurrency in outline
A go statement runs a function call concurrently on a cheap, growable stack; channels move values between goroutines and block until both sides are ready; sync.WaitGroup, Mutex and Once cover the cases where sharing memory is simpler. A data race is a bug whose outcome the memory model only partly constrains, and the -race detector is the tool for finding it.
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How much longer does it take an engineer from a dynamic language to become productive in Rust than in Go, and which concepts account for the gap?
Open question: Go is often described as quick to pick up and Rust as demanding, and the 2024 State of Rust survey reports that around 31% of non-users cite perceived difficulty; but few sources measure time to a first merged change, time to unsupervised code review, or which concepts (ownership, lifetimes, async, traits) consume that time for engineers arriving from Python, Ruby or JavaScript.
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Table-driven tests in Go with subtests
Write one test function that iterates over a slice of named cases and runs each with t.Run; the cases become data, a single case can be selected with go test -run 'TestX/name', and t.Parallel, t.Helper and t.Cleanup keep the loop fast and readable.
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Go race-detector coverage: a clean run says nothing about unexecuted paths
Tie go test -race results to the concurrent paths actually exercised, including startup and shutdown.
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Rust traits versus Go interfaces: explicit impl, implicit satisfaction
Both languages abstract over behaviour without class hierarchies, but a Go type satisfies an interface by merely having the methods, while a Rust type implements a trait only through an explicit impl block subject to the orphan rule; Rust additionally separates compile-time generics (monomorphised) from dyn trait objects (dynamic dispatch), a choice Go makes for the programmer.
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Go modules: go.mod, go.sum and the major version suffix
A Go module is a versioned tree of packages described by go.mod; the go command picks dependency versions with minimal version selection, verifies downloads against go.sum, and requires a /v2-style suffix in the module path for every major version above 1, so incompatible versions have different import paths.
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Go mutex copying: keep the lock identity with the state it protects
Audit value receivers, assignments and container operations that can copy a structure containing an active mutex.
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