Golang / GoLang Basics Interview Questions
1. What is Go and why was it created at Google?
Go (also called Golang) is an open-source, statically typed, compiled programming language designed at Google by Robert Griesemer, Rob Pike, and Ken Thompson. It was announced in 2009 and reached version 1.0 in 2012....
2. What are the key characteristics that make Go different from other popular languages?
Go has a deliberately small feature set. Every design decision was made by asking: does this add enough value to justify the complexity it introduces?...
3. What are packages in Go and what is special about the 'main' package?
Every Go source file starts with a package declaration. Packages are Go's unit of code organisation, encapsulation, and compilation....
4. What are the different ways to declare variables in Go?
Go offers several declaration styles. The choice between them is mostly about context (package level vs inside a function) and verbosity....
5. What are the fundamental data types in Go?
Go has a concise but complete set of built-in primitive types. Choosing the right type β especially between int and sized integers, and between float32 and float64 β matters for correctness and interoperability....
6. How do constants and iota work in Go?
Constants are declared with const and must be assigned a value that is computable at compile time β no function calls or runtime values. The iota identifier provides an automatically incrementing integer within a const block, resetting to 0 at...
7. How are functions defined in Go? What are variadic functions and named return values?
Functions are first-class citizens in Go β they can be assigned to variables, passed as arguments, and returned from other functions. Go functions support multiple return values (the primary mechanism for error handling), named returns, and variadic parameters....
8. How do if, for, and switch statements work in Go?
Go has a deliberately minimal set of control-flow constructs. There is only one loop keyword β for β which covers everything a while , do-while , and classic for loop does in other languages....
9. What is the difference between arrays and slices in Go?
Arrays and slices are both ordered sequences, but they work very differently. Arrays are value types with a fixed size baked into their type; slices are reference types that provide a flexible view into an underlying array....
10. How do maps work in Go? What are the key operations and pitfalls?
Maps are Go's built-in hash table. Keys must be comparable types (those that support == and != )....
11. How do structs work in Go and how do you attach methods to them?
Structs are Go's primary mechanism for grouping related data. Methods are functions with a receiver β the type they are attached to....
12. How do interfaces work in Go? How do you use type assertions and type switches?
An interface specifies a set of method signatures. Any type that implements all the methods satisfies the interface β implicitly, with no declaration....
13. What is the empty interface (any / interface{}) and when should you use it?
An interface with zero methods is satisfied by every type in Go. Written as interface{} or its alias any (Go 1.18+), it lets a variable or function parameter hold a value of any type....
14. How do pointers work in Go and how are they safer than C pointers?
Go has pointers β variables that store the memory address of another variable β but removes the dangerous parts of C pointers. There is no pointer arithmetic, no manual memory management, and the garbage collector handles deallocation....
15. How does Go handle errors, and what is the difference between %v and %w in fmt.Errorf?
Go treats errors as values returned by functions, not as exceptions thrown from the call stack. This makes error handling explicit and visible....
16. What are goroutines and how do you use sync.WaitGroup to wait for them?
A goroutine is a lightweight, concurrently executing function managed by the Go runtime. The cost to create one is ~2 KB of stack and ~300 ns β roughly 1000Γ cheaper than an OS thread....
17. What are channels in Go and what is the difference between buffered and unbuffered?
Channels are typed conduits for sending values between goroutines. They are goroutine-safe and provide the synchronisation primitive underlying Go's concurrency model.
18. How do defer, panic, and recover work together in Go?
defer schedules a function call to run when the surrounding function returns β regardless of how it returns (normally, via error, or via panic). It is Go's idiomatic resource-cleanup mechanism....
19. What are closures in Go and what is the loop variable capture gotcha?
A closure is a function that references and closes over variables from its surrounding scope. The closure captures the variable itself β not a copy of its value at the moment of creation....
20. What is the init() function and when does it run?
init() is an optional special function that runs automatically after all package-level variable initialisations β before main() . It takes no arguments, returns nothing, and cannot be called directly....
21. What is the Go module system? What do go.mod and go.sum contain?
Modules are Go's dependency management system (stable since Go 1.13). A module is a collection of related packages identified by a module path (typically a repository URL)....
22. What is a data race in Go and how do you detect one?
A data race occurs when two or more goroutines access the same memory location concurrently, at least one access is a write, and there is no synchronisation between them. Data races produce undefined, non-deterministic behaviour β results vary between runs...
23. What is the fmt.Stringer interface and how does it control how a type is printed?
The fmt package defines the Stringer interface: a type that implements String() string controls how it appears when printed with fmt.Println , fmt.Printf("%v") , and related functions. Implementing error works the same way for error messages....
24. What is the difference between a type definition and a type alias in Go?
Go has two ways to give a new name to a type, with importantly different semantics. Understanding this prevents subtle type-safety bugs and confusing compiler errors....
25. How does Go handle strings, runes, and bytes? Why is len(s) not the character count?
Go strings are immutable sequences of bytes stored in UTF-8 encoding. Since UTF-8 is a variable-width encoding, a single character (rune) can occupy 1 to 4 bytes....
26. What is a goroutine leak and what is the idiomatic way to prevent one?
A goroutine leak occurs when a goroutine is started but never terminates β it stays blocked forever waiting on a channel, mutex, or network call that will never complete. Goroutines are cheap but not free: leaked goroutines accumulate over time...
27. What is sync.Mutex and when do you use sync.RWMutex instead?
sync.Mutex provides mutual exclusion β at most one goroutine holds the lock at any moment. sync.RWMutex is an extension: multiple goroutines can hold a read lock simultaneously, but a write lock is exclusive....
28. How does struct embedding promote methods in Go, and how does it differ from inheritance?
Go uses composition through embedding rather than class inheritance. When a type is embedded (without a field name), its exported methods and fields are promoted to the outer type β they are directly accessible....
29. How does append() work internally in Go? When does it allocate new memory?
append adds elements to a slice. When there is spare capacity in the backing array, it writes directly into it and increments the length β no allocation....
30. What is context.Context and why is it the first parameter in so many Go functions?
context.Context is Go's standard mechanism for propagating three things across API boundaries and goroutine calls: cancellation signals , deadlines , and request-scoped values . Passing it as the first parameter is a Go convention β it allows any blocking call...
31. What is the 'typed nil' trap in Go and why does 'if err != nil' sometimes fail?
An interface value in Go has two components: a dynamic type and a dynamic value. An interface is nil only when BOTH are nil....
32. What are the most important formatting verbs in Go's fmt package?
Knowing fmt format verbs lets you produce clear output for debugging, logging, and user messages. The %v verb is the universal default; specialised verbs give more control....
