Ошибка	Последствие
Считать, что неинициализированная переменная держит мусор, как в C	На самом деле Go всегда обнуляет её до нулевого значения типа
Думать, что нулевая `string` — это `nil`	Это пустая `""`; `s == nil` даже не компилируется
Писать в `nil`-map без `make`	Чтение даёт ноль, а запись паникует `assignment to entry in nil map`
Использовать `:=` во вложенном блоке, не замечая затенения внешней переменной	Внешняя переменная не меняется — частый источник «потерянных» присваиваний и ошибок с `err`
Ждать, что `iota` пропустит значение на строке `_`	Строка `_` потребляет свой `iota`, сдвигая все последующие константы
Называть экспортируемую функцию со строчной буквы	Имя остаётся пакетно-приватным и не виден из других пакетов
Рассчитывать на неявное преобразование `int` в `float64`	Go требует явного `float64(x)` — иначе ошибка компиляции

beginner

Basics & Packages

Packages and imports, var/const/:= declarations, basic types, zero values, iota, identifier visibility, and the go build/run/mod tools.

go-basics

Practice: 9 questions · 1 task →

Sections

Contents

Detailed explanation

Basics & Packages

Go was designed as a small language that reads immediately: a handful of keywords, one way to declare a variable up front and a short := for locals, fixed-width basic types, and the go tool that builds, runs, and tests without a separate build system. Because of that simplicity the basics often slip by — "a package is a package, a variable is a variable."

Under the simple syntax sits the model interviews actually probe: a variable with no initializer gets not garbage but a strictly defined zero value; := in an inner scope can shadow an outer variable; a name is exported exactly when it starts with a capital letter; iota counts lines, not values. This topic walks the start of a program layer by layer — from packages and declarations to name visibility and the go commands.

Topic map

Packages & imports — a program is assembled from packages; package main and func main are the entry point, and an import pulls in other packages by path.
Declarations: var, const, := — var declares a variable (with or without a type), const an immutable constant, and := is short declaration with type inference inside a function.
Basic types — fixed-width integers and floats, bool, string; type conversion in Go is always explicit.
Zero values — a variable with no initializer gets its type's zero value (0, false, "", nil), useful by default.
iota and constants — the iota counter increments per line in a const block (counting _) and resets in a new block.
Names & visibility — a capital first letter makes a name exported (visible from other packages); lowercase keeps it package-private.
Build & run — go run, go build, go mod, and gofmt: how to build, run, and format a program.

Common mistakes and traps

Mistake	Consequence
Assuming an uninitialised variable holds garbage like in C	Go always zeroes it to the type's zero value
Thinking a zero-value `string` is `nil`	It is the empty `""`; `s == nil` does not even compile
Writing to a `nil` map without `make`	A read yields zero, a write panics `assignment to entry in nil map`
Using `:=` in a nested block without noticing it shadows the outer variable	The outer variable is unchanged — a common source of "lost" assignments and `err` bugs
Expecting `iota` to skip the value on a `_` line	A `_` line consumes its `iota`, shifting every later constant
Naming an exported function with a lowercase letter	The name stays package-private and is invisible from other packages
Relying on implicit `int` to `float64` conversion	Go requires an explicit `float64(x)` — otherwise a compile error

Why it matters for interviews

The basics are the junior-section filter: the question is never the syntax but the model under it. A candidate who learned "how to write it" but not "how it works" stumbles right here.

What interviewers usually check:

How var, const, and := differ and where each applies.
What zero value a variable with no initializer gets, and why a nil map cannot be written.
What iota is and how enums and bit flags are built from it.
How Go decides whether a name is exported (by the case of the first letter).
What go run, go build, and go mod do.

Why it matters

Every Go program starts from these basics, and this is exactly where a beginner's quietest bugs live — shadowing a variable with `:=`, writing to a nil map, confusing exported and unexported names. None of these fail at build time, but they surface in review and in interviews, where a junior question about zero values or `iota` filters out people who learned the syntax but not the model.

Ошибка	Последствие
Считать, что неинициализированная переменная держит мусор, как в C	На самом деле Go всегда обнуляет её до нулевого значения типа
Думать, что нулевая `string` — это `nil`	Это пустая `""`; `s == nil` даже не компилируется
Писать в `nil`-map без `make`	Чтение даёт ноль, а запись паникует `assignment to entry in nil map`
Использовать `:=` во вложенном блоке, не замечая затенения внешней переменной	Внешняя переменная не меняется — частый источник «потерянных» присваиваний и ошибок с `err`
Ждать, что `iota` пропустит значение на строке `_`	Строка `_` потребляет свой `iota`, сдвигая все последующие константы
Называть экспортируемую функцию со строчной буквы	Имя остаётся пакетно-приватным и не виден из других пакетов
Рассчитывать на неявное преобразование `int` в `float64`	Go требует явного `float64(x)` — иначе ошибка компиляции

beginner

Basics & Packages

Packages and imports, var/const/:= declarations, basic types, zero values, iota, identifier visibility, and the go build/run/mod tools.

go-basics

Practice: 9 questions · 1 task →

Sections

Contents

Detailed explanation

Basics & Packages

Topic map

Packages & imports — a program is assembled from packages; package main and func main are the entry point, and an import pulls in other packages by path.
Declarations: var, const, := — var declares a variable (with or without a type), const an immutable constant, and := is short declaration with type inference inside a function.
Basic types — fixed-width integers and floats, bool, string; type conversion in Go is always explicit.
Zero values — a variable with no initializer gets its type's zero value (0, false, "", nil), useful by default.
iota and constants — the iota counter increments per line in a const block (counting _) and resets in a new block.
Names & visibility — a capital first letter makes a name exported (visible from other packages); lowercase keeps it package-private.
Build & run — go run, go build, go mod, and gofmt: how to build, run, and format a program.

Common mistakes and traps

Mistake	Consequence
Assuming an uninitialised variable holds garbage like in C	Go always zeroes it to the type's zero value
Thinking a zero-value `string` is `nil`	It is the empty `""`; `s == nil` does not even compile
Writing to a `nil` map without `make`	A read yields zero, a write panics `assignment to entry in nil map`
Using `:=` in a nested block without noticing it shadows the outer variable	The outer variable is unchanged — a common source of "lost" assignments and `err` bugs
Expecting `iota` to skip the value on a `_` line	A `_` line consumes its `iota`, shifting every later constant
Naming an exported function with a lowercase letter	The name stays package-private and is invisible from other packages
Relying on implicit `int` to `float64` conversion	Go requires an explicit `float64(x)` — otherwise a compile error

Why it matters for interviews

The basics are the junior-section filter: the question is never the syntax but the model under it. A candidate who learned "how to write it" but not "how it works" stumbles right here.

What interviewers usually check:

How var, const, and := differ and where each applies.
What zero value a variable with no initializer gets, and why a nil map cannot be written.
What iota is and how enums and bit flags are built from it.
How Go decides whether a name is exported (by the case of the first letter).
What go run, go build, and go mod do.

Why it matters

Основы и пакеты

Основы и пакеты

Карта темы

Частые ошибки и ловушки

Значение для собеседований

Basics & Packages

Basics & Packages

Topic map

Common mistakes and traps

Why it matters for interviews

Основы и пакеты

Основы и пакеты

Карта темы

Частые ошибки и ловушки

Значение для собеседований

Basics & Packages

Basics & Packages

Topic map

Common mistakes and traps

Why it matters for interviews