Getting Started

Question 1

How to declare a variable in go and initialize it with a value?

Answer 1

var i int = 10

Question 2

Can go infer types? How to declare a variable with an inferred type?

Answer 2

yes.

name := “Jhon Doe”

Question 3

How to declare a pointer of a string? What is the default value of an empty pointer (pointer that doesn’t point to anything)?

Answer 3

var name *string

nil

Question 4

What is de-referencing in go? How to dereference a string?

Answer 4

Is accessing the actual pointer content instead of the address.
*name = “Jhon Doe”

Question 5

What happens if I try to dereference a pointer that was not initialized? How to fix?

Answer 5

It will throw the invalid memory address or nil pointer dereference error.
var name *string = new(string)

Question 6

What is fmt.Println(name) output? How to output the content?

Answer 6

The pointer’s memory address (e.g: 0x123beef)

By dereferencing fmt.Println(*name)

Question 7

What is pointer arithmetic? Does golang support that? Why?

Answer 7

Is manipulating the memory location fmt.Println(*(name) + 1). Golang doesn’t support that because it is too error prone.

Question 8

How can I grab the address of a variable in go?

Answer 8

ptr := &name

Question 9

What is an implicit-typed constant in go?

Answer 9

Is a constant value that will adjust itself to match the operation (e.g: const +1 and const + 1.2).

Question 10

Should I define the value of a const in the same line of the declaration? How does it look like?

Answer 10

Yes. const c = 3

Question 11

Can I define a type in a constant? What happens then?

Answer 11

Yes. The type is checked.

Question 12

What is iota? When does it resets?

Answer 12

Is an unique-automatic-increment value that can be used in compile time. Resets in a new const() block.

Question 13

Do I have to re-state iota everytime?

Answer 13

No. When not specified below an iota, the other consts will get iota automatically.

Question 14

Can a const use the return value of a function?

Answer 14

no. consts can only be assigned with compile-time stuff - NOT runtime.

Question 15

What replaces a class in go?

Answer 15

struct

Question 16

What is an array in golang? How to declare one and set value?

Answer 16

A fixed-size and same-type list of elements.
var arr [3] int //arr := [3]int{1,2,3}
arr[0] = 1

Question 17

What is a slice? Does it have a copy of the array? How to declare one

Answer 17

Is the full array or a part of the array. Does not contain a copy of the values (changes the sliced array).

slice = arr[:]

Question 18

Can I use slice to create a non-fixes size array? How to declare one? How to add a value to the slice?

Answer 18

Yes.
slice := []int{1,2,3}
append(slice, 4)

Question 19

How to get a slice of the array using start and end (BUT NOT INCLUDING) positions?

Answer 19

slice2 := slice[1:2] // read the second element only because it reads until 2 but NOT including 2

Question 20

How to declare a hash table that has a key of string and value of int in go?

Answer 20

map := map[string]int

Question 21

What is the only heterogeneous type on golang? What does it mean?

Answer 21

struct. It can hold different types of data.

Question 22

Can I add fields to a struct in run time?

Answer 22

No. Compile time only

Question 23

how to declare a struct?

Answer 23

type user struct {
  ID int
  FirstName string
  LasrName string
}

Question 24

How to use the user struct?

Answer 24

var u user;

Question 25

What is the so called implicit initialization syntax? What is the symbol used? Example of one.

Answer 25

Means I can create a variable without declaring its type.
:=
user := user{1, “Erikson”, “asd”}

Question 26

Where can I create a struct?

Answer 26

Anywhere: in the function scope, package scope and etc,

Question 27

How files are associated with a module?

Answer 27

All the .go files in the same directory or below a go.mod file is part of the same module.

Question 28

What is a package?

Answer 28

Is the a code grouping (namespace?) mechanism. A module can have many of these.

Question 29

What is the first thing I need to do when creating a go file?

Answer 29

Declaring the package (namespace)

Question 30

What happens if I create a file in a subdirectory?

Answer 30

vscode will suggest it as the package name

Question 31

Can my package have its own (static) variables declared? How? What happens to the implicit initialization syntax?

Answer 31

Yes.
var (
  user []*User
  nextID = 1
)
it becomes "=" again

Question 32

What is a multi-line initialization syntax? What is special about that?

Answer 32

u := models.User {
  ID: 2,
  first: "Erikson",
  last: "asd", // < you need to add this comma here
}

need to add a comma at the end of the last line

Question 33

How to use a struct called User from a model called models?

Answer 33

u := models.User{}

Question 34

What happens to the go executable created with the go run command?

Answer 34

It is thrown away after the execution is completed?

Question 35

How to create a persistent executable?

Answer 35

go build

Question 36

Is it common to raise exceptions with go? How is it done?

Answer 36

No. Most functions when called return the expected result (assigned when works) and the error (assigned when does not work).

Question 37

How to discard a result of a function in go?

Answer 37

_, err := doSomething()

Question 38

How to add a method to a struct in go? Is this similar to what concept on .net?

Answer 38

You need to add a function OUTSIDE the struct itself since structs only holds data structures.

The function will have a special start that is func (u User) getFullName() string;

Similar to extension methods in .net (but replace the this keyword by the first parenthesis).

Question 39

How to associate related behaviors together in go?

Answer 39

create an empty struct then created the “extension methods”

Question 40

How to create a constructor in go? Is it supported?

Answer 40

create a function that start with the name new.. e.g: func newUser() *User. There’s no official support for constructors, this is just a trick.

Question 41

What happens if I return a pointer to a locally created struct in go?

Answer 41

go will notice that and will promote that pointer to the heap.

Question 42

How to implement an interface in go? Do I need a special statement for that?

Answer 42

just create a method that matches the interface’s method signature. No special statement.

Question 43

What is a mux? What is its full name?

Answer 43

Is a device that selects between several analog or digital input signals and forwards the selected input to a single output line.

Multiplexor

Question 44

does break and continue (within a for) statements work on golang?

Answer 44

yes.

Question 45

What does the range statement does?

Answer 45

Returns the index and the value in that index

Question 46

What does the panic statement does?

Answer 46

Halts the application and prints the panic message with some tracing.

Question 47

Is panic state recoverable?

Answer 47

Yes.

Question 48

Do I need to explicitly call break after a condition is hit on a switch block? How to skip the break and go to the next condition as well?

Answer 48

No. The break is implicitly there. Add the fallthrough statement

Question 49

How to add a condition to the switch that happens when none matches?

Answer 49

default: