Quiz yourself in Golang. Part 1

30 basic questions to measure your Golang knowledge. Answers and .go files you can find on GitHub page.

Don’t hesitate to create a Pull Request in case of some found errors, typos.

What’s the output of the following code?

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package main

import "fmt"

const (
	a = iota
	b = iota
	c = iota
)

const (
	d, e, f = iota, iota, iota
)

func main() {
	fmt.Println(a, b, c, d, e, f)
}

• a. 0 1 2 3 4 5
• b. 0 1 2 0 1 2
• c. 0 1 2 0 0 0
• d. 0 0 0 0 1 2

What verb should we use with fmt.Printf to print boolean?

• a. %v
• b. %t
• c. %b
• d. %s

Does Go support type inheritance?

• a. Yes
• b. No

Is it possible to declare multiple types of variables in single declaration in Go?

var a, b, c = 3, 4, “foo”

• a. Yes
• b. No

Is it possible to make package content directly accessible without need to be preceed by “fmt.”?

• a. Yes. import “fmt”
• b. Yes. import _ “fmt”
• c. Yes. import . “fmt”
• d. No

Is it possible to have multiple tag strings in struct field?

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package main

import (
	"fmt"
	"reflect"
)

func main() {
	type User struct {
		Name string `key:"name"`
	}

	u := User{}
	st := reflect.TypeOf(u)
	field := st.Field(0)
	fmt.Println(field.Tag.Get("key"))
}

• a. Yes. They should be comma-separated: key:"name",maxlength:"128"
• b. Yes. They should be space-separated: key:"name" maxlength:"128"
• c. No

What is the output of the following code?

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package main

import "fmt"

func main() {
	for i := 0; i < 4; i++ {
		defer fmt.Print(i)
	}
}

• a. 0123
• b. 3210
• c. 0000
• d. 3333

What characters is go fmt command using for indent?

• a. 4 spaces
• b. 2 spaces
• c. tab character
• d. it’s configurable

Choose the correct statement regarding the output of the following code.

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package main

import "fmt"

func main() {
	tagsViews := map[string]int{
		"unix":   0,
		"python": 1,
		"go":     2,
		"golang": 3,
		"devops": 4,
		"gc":     5,
	}
	for key, views := range tagsViews {
		fmt.Println("There are", views, "views for", key)
	}
}

• a. Output will be ordered by values
• b. Output will be ordered by keys
• c. Output will be ordered randomly
• d. Output will be ordered by position in the code

How can we change the value of GOMAXPROCS in Go?

• a. Via environment variable GOMAXPROCS
• b. In the code
• c. a and b
• d. Impossible as it’s equal to the number of available CPUs

Which is the slowest concatenation method from the list?

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package main

import (
	"bytes"
	"fmt"
	"strings"
)

func main() {
	// 1
	s := ""
	for i := 0; i < 5; i++ {
		s += "a"
	}
	fmt.Println(s)

	// 2
	var buffer bytes.Buffer
	for i := 0; i < 5; i++ {
		buffer.WriteString("a")
	}
	fmt.Println(buffer.String())

	// 3
	sl := []string{"a", "a", "a", "a", "a"}
	fmt.Printf(strings.Join(sl, ""))
}

• a. 1
• b. 2
• c. 3

What’s the output of the following code?

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package main

import "fmt"

func main() {
	var a int8 = 3
	var b int16 = 4

	sum := a + b

	fmt.Println(sum)
}

• a. 7
• b. 4
• c. 3
• d. invalid operation: a + b (mismatched types int8 and int16)

Where should we use defer in the following code?

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package main

import "os"

func main() {
	src, err := os.Open("filename")
	// 1
	//defer src.Close()
	if err != nil {
		return
	}

	// 2
	//defer src.Close()

	src.WriteString("Hello")

	// 3
	//defer src.Close()
}

• a. 1
• b. 2
• c. 3
• d. None of them

On what data types you can use “for - range” statement?

• a. array, slice, map
• b. array, slice, map, string
• c. slice, map, string
• d. slice, map

Does Go support optional parameters in functions?

• a. Yes
• b. No

When will init() function be called?

• a. Before main() function in main package
• b. After importing a package with defined init() function
• c. Only when you call it
• d. a and b

Does Go have a ternary operator?

• a. Yes
• b. No

Is it possible to check if the slices are equal with “==” operator or not?

• a. Yes
• b. No

What is the size of the following struct?

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package main

import "fmt"
import "unsafe"

func main() {
	s := struct {
		A float32
		B string
	}{0, "go"}

	fmt.Printf("%T, %d\n", s, unsafe.Sizeof(s))
}

• a. 12
• b. 8
• c. 24
• d. 32

What’s the default buffer size of the channel in Go?

• a. 0
• b. 1
• c. No default size

What are the default values of these types: string,*string ?

• a. “”, nil
• b. “”, ""
• c. nil, nil
• d. nil, ""

Is it possible to define constant of an array type float32?

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package main

import "fmt"

const array = []float32{0.1, 0.2, 0.3}

func main() {
	fmt.Printf("%v", array)
}

• a. Yes
• b. No

Can short declaration “:=” be used for defining global variables?

• a. Yes
• b. No

In Go, does a break statement exit from a select block?

• a. Yes
• b. No

Which one of the following is correct?

• a. const Pi = math.Pi
• b. const Pi = 3.14
• c. both a and b are correct
• d. None of the above

Arrays are value types. In case of arrays perform as arguments, functions get their copies instead of a reference. Don’t they?

• a. Yes
• b. No

Which of the following variables are exportable from another external package?

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package main

var (
	aName string

	BigBro string

	爱 string
)

func main() {

}

• a. aName, BigBro
• b. BigBro
• c. aName, BigBro, 爱
• d. BigBro, 爱

What’s the sequence for the output of the following code?

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package main

import (
	"fmt"
	"sync"
	"time"
)

func main() {
	var wg sync.WaitGroup

	wg.Add(1)
	go func() {
		time.Sleep(time.Second * 2)
		fmt.Println("1")
		wg.Done()
	}()

	go func() {
		fmt.Println("2")
	}()

	wg.Wait()
	fmt.Println("3")
}

• a. 3 2 1
• b. 1 2 3
• c. 2 3 1
• d. 2 1 3

How to compile the following code to the binary file with name “eight”?

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package main

import "fmt"

func main() {
	fmt.Println("Hi")
}

• a. go build 8.go eight
• b. go build -o eight 8.go
• c. go build 8.go -o eight

Can we set DEBUG=true with go build?

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package main

import (
	"fmt"
)

var DEBUG bool

func main() {
	fmt.Printf("DEBUG is %t\n", DEBUG)
}

• a. Yes. go build -ldflags ‘-X main.DEBUG=true’ 9/9.go
• b. No