16 Go interview questions on go idioms, design patterns & language design, with detailed answers and code.
Functional options are variadic functions of type func(*T) (or func(*T) error ) applied to a value that already holds defaults. The constructor stays backward-compatible…
Package-level var / init() runs eagerly and in a single thread before main , so it is thread-safe with no extra work. The cost is startup time and side effects (network,…
Define a named integer type and a const block that uses iota . Go does not have closed enums: Status(42) compiles, and untyped constants convert implicitly, so…
Inside the function, a variadic parameter xs ...int is a []int . A call like f(1, 2, 3) allocates a new slice. A call like f(s...) passes the caller's slice header as is…
A closure captures variables , not values, by reference. It sees later writes, and its own writes are visible outside. If the closure outlives the stack frame (it is…
Go's designers value code that is easy to read and maintain at scale, where every call site is unambiguous, over expressive power. Each missing feature has an idiomatic…
Func values can only be compared to nil . f == g is a compile error ("func can only be compared to nil"), and map[func()]int is "invalid map key type". The reason:…
No. The Go compiler does not guarantee tail-call elimination and in practice doesn't do it, partly to keep stack traces complete. Each recursive call uses a stack frame.…
A common layout: cmd/<binary>/main.go holds thin mains that only do wiring. internal/ holds most of the code; the compiler enforces that only code rooted at internal's…
Idiomatic DI in Go means constructors that accept interfaces or concrete dependencies as parameters , all wired explicitly in main . No container is needed. The…
In Go these patterns usually collapse into small interfaces plus function types , with no class hierarchies. // Strategy: behavior chosen at runtime through an interface…
A circuit breaker is a state machine. Closed : calls pass and failures are counted. Open : calls fail fast until a cooldown ends. Half-Open : a limited number of probe…
_ is a write-only placeholder. Anything assigned to it is discarded, and it never creates a binding. import ( _ "embed" // needed for //go:embed on string/[]byte vars _…
An anonymous struct is a struct type written inline without a name. Struct tags are raw string metadata on fields, read through reflection ( reflect.StructTag.Get ) by…
The client sends an Idempotency-Key header (a UUID) with non-idempotent requests such as POST. The server atomically reserves the key, runs the operation once, stores…
Concurrency: Go has goroutines on an M:N scheduler plus channels. Blocking-style code scales to 100k+ tasks without function coloring. Java 21+ virtual threads get…