// 18 Essential Go Interview Questions

1. Go code was created with practicality, unlike other languages that began as intellectual exercises. Every choice in syntax and feature is made at the programmer's convenience.
2. Golang is scale-efficient and concurrency-optimized. Since concurrent programming is taken very seriously in Go, it is a powerful tool to hunt down those race conditions. It is fully integrated into Go’s toolchain.
3. Due to its one standard code structure, Golang is frequently seen as being more readable than other languages.
4. Since automatic garbage collection runs concurrently with the programme, it is far more effective than Java or Python.

Now, moving onto an example, one of the main domains where the use of Golang is beneficial is cloud-native applications. The architecture of modern digital software must include cloud computing. Software systems that are easily scalable and shareable using cloud services can be created with ease using Go.

Additionally, Golang is a fantastic choice for creating microservices and cloud-native software. Being a cutting-edge cross-platform programming language, it enables you to build dependable and adaptable cloud apps swiftly.

To meet the specific needs of your clients, you can create a Go application in Kubernetes utilizing Docker containerization. You can also obtain auto-scaling and multi-cluster capability because Kubernetes is written in Go.

The Go language has different interfaces as compared to other languages. In the Go programming language, the interface is a specific type that specifies a collection of one or more method signatures. The interface cannot be created since it is abstract.

However, you are allowed to create an interface type variable and give it a value of a concrete type by using the required interface methods. In other words, the interface is a new type as well as a collection of methods.

Therefore, interfaces effectively serve as placeholders for methods with different implementations depending on the object that uses them.

For instance, you could create a geometry interface that requires area() and circumference() implementations for any shapes that use it:

type geometry interface {
    area() float64
    circumference() float64
}

package main

import "fmt"

func main() {
   fmt.Println(swap())
}

func swap() []int {
      a, b := 11, 25
   b, a = a, b
   return []int{a, b}
}

Without using a temporary variable, this code switches the values of two variables. By doing this, the code can change the values of two variables without requiring a third.

Go Pointers are variables that store any variable's address. They are referred to as special variables as a result. Pointers support two operators:

1. The value in the address the pointer stores is accessed via the * operator, also known as a dereferencing operator.
2. The variable's address kept in the pointer is returned using the & operator, also known as the address operator.

The method can directly alter the value provided to it thanks to pointers. By doing so, pass-by-reference functionality is achieved. In the presence of a huge data structure, they improve performance in edge cases. Pointers make it easier to copy vast amounts of data quickly.

It aids in illustrating the absence of values. For instance, it is useful to know if a key is present or absent when unmarshalling JSON data into a struct; otherwise, the key is present but has a value of 0.

Note: Commonly asked Golang interview question.

Goroutines communicate with one another by using the Go channel. It is a method for transferring data to other goroutines. The same type of data can be transferred across a channel. The channel's data flow is bidirectional, allowing goroutines to send and receive data over the same channel.

By including the chan keyword as demonstrated in the following syntax, a channel can be created:

var channel_name chan Type

A channel can also be created by using the make() function as:

channel_name:= make(chan Type)

To send the data to a channel, we can use the <- operator as shown in the syntax:

channel_name <- element

To receive data sent by the send operator, we can use the below syntax:

element := <-Mychannel

Note: Commonly asked Golang interview question.

When there is an empty slot on the buffered channel, the transmitter will block, and when the channel is empty, the receiver will block.

The sender will block an unbuffered channel it until the recipient receives its data. The receiver will simultaneously block the channel until the sender inserts data into it.

The directories that are part of $GoROOT, which mixes the source code and binary files for Go Projects, are represented by the environment variable GoPATH.

The GoROOT variable determines the Go SDK's location. We do not have to modify the variable unless we plan to use multiple Go versions.

The GoPATH determines the workspace's root, whereas the GoROOT determines the location of Go SDK.

Note: Commonly asked Golang interview question.

Go code is contained in a workspace. Three directories are found at the root of a workspace's directory hierarchy.

Here are a few instances:

• The "src" directory houses packages of GO source files.
• Package objects are located in the "pkg" directory.
• A directory called "bin" contains executable commands.

No, Go follows a different strategy. Go's multi-value returns make it simple to report an issue without overloading the return result for simple error handling. Error-values are used in Go programs to denote aberrant conditions.

Example:

func Open(name string) (file *File, err error)
f, err := os.Open("file.txt")
if err != nil {
    log.Fatal(err)
}

Note: Commonly asked Golang interview question.

Consider the following example:

if val, ok := dict["duck"]; ok {
    //do something here
}

In Go, if clauses may also contain an initialization clause and a condition. The example up top makes use of both.

Two variables are first initialized by the code. ok will receive a bool that will be set to true if "duck" was present in the map, and val will receive either the value of "duck" from the map or a "zero value" (in this example, the empty string).

The body of the if statement will be carried out, and val will be local to that scope if "duck" is in fact present in the map. This verifies whether the map contains a key in Go.

Note: Commonly asked Golang interview question.

Despite supporting object-oriented programming and containing types and functions, there is no type hierarchy in Go. This contrasts with most object-oriented languages, including Python and Ruby, as well as dynamic languages like C++, Java, C#, and Scala.

Yes, you can use structures, methods, encapsulation, and inheritance in Go, but differently.

Classes in other languages fulfill comparable functions, as do structural types (methods). In Go, methods are functions that work with specific types. They have a receiver clause that specifies the type of business they can conduct.

We can embed different anonymous types inside of one another. When we embed a nameless struct, the embedded struct immediately gives the embedding struct access to its state (and methods).

Types that specify sets of methods are called interfaces. They lack implementation, much like other languages' interfaces. All-interface-method-implementing objects automatically implement the interface. There is no subclassing, inheritance, or "implements" keyword.

The package level is where Go encapsulates things. Only those names that begin with a lowercase letter are displayed in that package. In a private package, you can conceal everything and just expose particular types, interfaces, and factory functions.

Implementation inheritance is similar to composition by anonymous type embedding.

Last, any value that implements the interface can be stored in an interface variable. In Go, polymorphism is accomplished using this interface attribute.

Packages (pkg) are the directories in your Go workspace that house other packages or Go source code.

Your source files' functions, variables, and types are all kept in the linked package. Each Go source file is part of a package, which is identified at the beginning of the file by:

package <packagename>

One can import and export packages to reuse existing functions or types using:

import <packagename>

Golang’s standard package, fmt, contains formatting and printing functions such as Println() and Sprintf().

A goroutine is a function or method that runs concurrently with any other function or method, or any other goroutine. Most Golang programs use thousands of goroutines at once because they are lighter than conventional threads.

Add the go keyword before the function definition to create a goroutine.

go f(x, y, z)

A goroutine can be stopped by sending it a signal channel. Checks must be placed logically, such as near the front of your for loop, because goroutines can only react to signals if instructed.

package main
import (
    "fmt"
    "time"
)
func f(from string) {
    for i := 0; i < 5; i++ {
        fmt.Println(from, ":", i)
    }
}
func main() {

    f("direct")
    go f("goroutine")
    go func(msg string) {
        fmt.Println(msg)
    }("going")

    time.Sleep(time.Second)
    fmt.Println("done")
}

Running this code would give us the following output:

direct : 0
direct : 1
direct : 2
direct : 3
direct : 4
direct : 5
goroutine : 0
going
goroutine : 1
goroutine : 2
goroutine : 3
goroutine : 4
goroutine : 5
done

Goroutines have the advantage of existing in a virtual environment created by the Go runtime rather than being reliant on the underlying operating system. As a result, a goroutine's optimizations are less dependent on the platform on which they are operating.

Note: Commonly asked Golang interview question.

Since Golang does not provide classes, inheritance is not possible.

To establish the initial behaviour of a new object, composition can be used to simulate inheritance behaviour using an existing struct object. Beyond the original struct, functionality of the new object can be expanded.

type Animal struct {
    // ...
}

func (a *Animal) Eat()   { ... }
func (a *Animal) Sleep() { ... }
func (a *Animal) Run() { ... }

type Cat struct {
    Animal
    // ...
}

In the above snippet, the operations Eat(), Sleep(), and Run() are included in the Animal struct. These functions are integrated into the child struct Cat by simply placing the struct at the top of the Cat implementation.

The concatenation operator (+), which enables you to add strings like you would add numerical values, is the simplest technique to concatenate strings.

Here’s how it works:

package main
import "fmt"
  
func main() { 
  
    // creating and initializing strings 
    // using var keyword 
    var str1 string 
    str1 = "Hello "
  
    var str2 string 
    str2 = "World!"
  
    fmt.Println("String 1: ", str1+str2) 
  
    // creating and initializing strings 
    // using shorthand declaration 
    str3 := "Welcome"
    str4 := "Go Interview Questions"
  
    result := str3 + " to " + str4 
  
    fmt.Println("String 2: ", result) 
}  

Any Golang constant, whether named or unnamed, is untyped unless expressly given a type. An untyped floating-point constant, such as 4.5, can be used everywhere such a number is permitted. Up to their evaluation in a type-demanding expression, we can temporarily avoid Go's strong type system by using untyped constants.

// untyped integer constant
const a = 1
var myFloat32 float32 = 4.5
var myComplex64 complex64 = 4.5

When the type is explicitly stated in the declaration, constants are typed. When using typed constants, you cannot assign them to variables of any type or combine them with other constants in mathematical operations, as is possible with untyped constants.

const typedInt int = 1

Generally, a constant's type should only be declared when essential. If not, simply declare constants without specifying a type.

In Go, := is used for both assignment and declaration, whereas = is solely used for assignment.

For instance, num:= 10 and var num int = 10 are equivalent.

Using := is not permitted outside of functions. A statement outside of a function should begin with a keyword. In the same scope, you may not utilize them more than once:

age := 42
age := 42 // <-- error

Since using := twice does not redeclare a second variable because it introduces "a new variable," it is against the law.

Note: Commonly asked Golang interview question.

Slices are used a lot in this code. Slices, instead of arrays, are solely typed by the elements they contain (not the number of elements). Use the built-in make to produce an empty slice with a length that is not zero. Here, we cut three-string segments (initially zero-valued).

Similar to how we can set and get with arrays. Len gives the anticipated slice length.

Slices offer several additional operations in addition to these fundamental ones, making them richer than arrays. The built-in add is one option; it returns a slice with one or more new values. Because we might receive a new slice value from append, take note that we must accept a return value.

Therefore, the result would be:

emp: [  ]
set: [a b c]
get: c
len: 3
apd: [a b c d e f]

Golang allows for package testing that is automated using unique testing suites.

Establish a file with the extension _test.go that contains the function TestXxx and the name of the feature you're testing in place of Xxx to create a new suite. For instance, TestSignup would be used to test the signup functionality.

The testing suite file is then inserted into the package with the file you want to test. Regular execution will skip the test file, but the go test command will execute it.