Go Language Interview Questions and Answers for 4 Years of Experience

If you are preparing for a Go (Golang) interview for a Senior Software Engineer role with 4 years of experience, you can expect questions related to Concurrency, Goroutines, Channels, Mutexes, and Core Go Concepts. This blog will provide a detailed list of frequently asked questions along with well-explained answers to help you ace your interview.

1. How does Go handle concurrency?

Answer:

Go provides lightweight threads called Goroutines and channels to handle concurrency efficiently. The Go runtime scheduler manages Goroutines instead of relying on OS threads.

Example:

package main

import (
    "fmt""time"
)

func sayHello() {
    fmt.Println("Hello, Goroutine!")
}

func main() {
    go sayHello() // Starts a Goroutine
    time.Sleep(time.Second) // Ensures main doesn't exit before Goroutine runs
}

Key Points:

• Goroutines are lightweight compared to OS threads.
• The go keyword is used to start a Goroutine.
• Go runtime schedules Goroutines dynamically.

2. What are channels in Go? How do they help in concurrency?

Answer:

Channels in Go provide a way for Goroutines to communicate and synchronize execution. They prevent race conditions by ensuring data exchange happens safely between Goroutines.

Example:

package main

import "fmt"

func sendData(ch chan string) {
    ch <- "Hello, Channel!" // Send data
}

func main() {
    ch := make(chan string) // Create a channelgo sendData(ch)         // Start Goroutine
    fmt.Println(<-ch)       // Receive data
}

Types of Channels:

1. Unbuffered Channels - Synchronizes sender and receiver.
2. Buffered Channels - Stores values, sender doesn’t block immediately.

3. How to print numbers 1 to 10 using two Goroutines (one prints odd, one prints even)?

Answer:

This problem requires synchronization between two Goroutines to print numbers in order.

Go Code:

package main

import "fmt"

func main() {
    numChan := make(chan bool) // Sync channel
    done := make(chan bool)    // Completion signal

    go func() {
        for i := 1; i <= 9; i += 2 {
            <-numChan
            fmt.Println(i)
            numChan <- true
        }
    }()

    numChan <- truego func() {
        for i := 2; i <= 10; i += 2 {
            <-numChan
            fmt.Println(i)
            if i == 10 {
                done <- truereturn
            }
            numChan <- true
        }
    }()

    
    <-done
}

Key Points:

• Uses a single channel for synchronization.
• Ensures correct order of execution.
• Blocks main function until execution is complete.

4. What are Mutexes in Go? What are the different types?

Answer:

Mutex (Mutual Exclusion Lock) is used to prevent race conditions when multiple Goroutines access shared data.

Types of Mutexes:

1. sync.Mutex - Blocks concurrent access to a resource.
2. sync.RWMutex - Allows multiple readers but only one writer.

Example Using sync.Mutex:

package main

import (
    "fmt""sync"
)

var count int
var mu sync.Mutex

func increment(wg *sync.WaitGroup) {
    defer wg.Done()
    mu.Lock()
    count++
    fmt.Println("Count:", count)
    mu.Unlock()
}

func main() {
    var wg sync.WaitGroup
    wg.Add(2)
    go increment(&wg)
    go increment(&wg)
    wg.Wait()
}

Example Using sync.RWMutex:

package main

import (
    "fmt""sync"
)

var count int
var rwMu sync.RWMutex

func read(wg *sync.WaitGroup) {
    defer wg.Done()
    rwMu.RLock()
    fmt.Println("Reading Count:", count)
    rwMu.RUnlock()
}

func write(wg *sync.WaitGroup) {
    defer wg.Done()
    rwMu.Lock()
    count++
    fmt.Println("Updated Count:", count)
    rwMu.Unlock()
}

func main() {
    var wg sync.WaitGroup
    wg.Add(3)
    go read(&wg)
    go read(&wg)
    go write(&wg)
    wg.Wait()
}

Key Takeaways:

• Use sync.Mutex when only one Goroutine should modify shared data.
• Use sync.RWMutex when multiple readers are allowed but only one writer.

5. How does defer work in Go? Provide an example.

Answer:

The defer statement delays execution of a function until the surrounding function returns.

Example:

package main

import "fmt"

func main() {
    fmt.Println(1)
    defer fmt.Println(2)
    fmt.Println(3)
    defer fmt.Println(4)
    fmt.Println(5)
    defer fmt.Println(6)
}

Expected Output:

1
3
5
6
4
2

Key Points:

• Deferred calls execute in LIFO order (Last In, First Out).
• Useful for resource cleanup (e.g., closing files, unlocking mutexes).

Conclusion

If you’re preparing for a Golang interview with 4 years of experience, focus on Concurrency, Goroutines, Channels, Mutexes, and Defer Statements. Understanding these concepts will help you perform well in real-world system design problems.

Good luck with your interview! 🚀