Question 1

What is the correct syntax to declare a variable in Go?

Accepted Answer

In Go, there are three main ways to declare a variable: var x int (explicit declaration with type), var x = 10 (declaration with type inference), and x := 10 (short declaration with inference, only inside functions). The short form := is most commonly used for local variables as it is concise and idiomatic.

Question 2

What is a slice in Go?

Accepted Answer

A slice is a dynamic view over an underlying array that allows manipulation of variable-length sequences of elements. Unlike arrays which have a fixed size defined at compile time, slices can grow or shrink dynamically through operations like append. This flexibility makes them the most commonly used sequential data structure in Go for storing collections of homogeneous elements.

Question 3

What is an interface in Go?

Accepted Answer

An interface in Go is a type that defines a set of method signatures. A type implements an interface implicitly by defining all its methods, without explicit declaration. This enables strong decoupling and flexibility in Go program design.

Question 4

What is the interface used to represent errors in Go?

Accepted Answer

The error interface is the predefined interface in Go to represent error conditions. It contains a single Error() method that returns a string describing the error. The nil value represents no error. This is the conventional interface used by all standard library packages and Go developers to signal and propagate errors.

Question 5

Which function allows encoding a Go struct into JSON?

Accepted Answer

json.Marshal encodes a Go struct into JSON bytes. This function reads struct tags to customize serialization (renaming, field omission). For streaming to io.Writer, using json.NewEncoder avoids creating an intermediate buffer in memory.

Question 6

What is the main difference between DB.Query and DB.Exec?

Accepted Answer

DB.Query is used to execute SELECT queries that return rows of data, while DB.Exec is for executing SQL commands that don't return results (INSERT, UPDATE, DELETE). Query returns a Rows object that must be iterated and closed with rows.Close(), whereas Exec returns a Result containing the number of affected rows and the last inserted ID.

Question 7

What is the main role of the context package in Go?

Accepted Answer

The context package allows managing timeouts, cancellations and deadlines consistently across the entire call chain. This prevents zombie goroutines that continue running when their result is no longer needed. Always pass the context as the first parameter and regularly check Done() in long operations to respect cancellations.

Question 8

What is the reflect package in Go?

Accepted Answer

The reflect package allows inspecting and manipulating types and values at runtime. It is used to implement generic libraries (JSON marshaling, ORM), but its direct use in application code is discouraged as it sacrifices type safety and performance.

Question 9

What is the main difference between stack and heap allocation in Go?

Accepted Answer

The stack is managed automatically and allocations are extremely fast (simple stack pointer movement). Variables on the stack are automatically freed when the function returns. The heap requires the garbage collector to free memory and allocations are slower as they involve the Go runtime. Variables that survive beyond the function or whose size is not known at compile time go on the heap.

Question 10

What is the pprof tool in Go?

Accepted Answer

pprof is Go's built-in profiling tool that analyzes CPU, memory, goroutines and other metrics. It generates binary format profiles that can be analyzed with go tool pprof. This tool is essential for identifying performance bottlenecks and optimizing Go applications in production.

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