The Go Standard Library

Question 1

What are the two ways to print data to the console app? What are the diffs?

Answer 1

println and printf. Printf will format and replace value of %v, won’t break line, needs a \n

Question 2

How to printf with float?

Answer 2

%.2f

Question 3

What is the difference between a flag and an arg? How to add a flag to our app?

Answer 3

Flags are named and args are arbitrary.

flag. String(“flagName”, “defOption”, “Description”)
flag. Parse

Question 4

How to read keyboard input? When the input is read and the function returns?

Answer 4

fmt.Scanf

When the user press enter (\n)

Question 5

How to read a text file for example?

Answer 5

bufio.NewScanner(file via os.Open)

Scanner.Scan {}

Question 6

What does the fmt package do?

Answer 6

Format input and output text of our application. Can add padding and colors for example.

Question 7

What does fmt.sscanf do?

Answer 7

get text from specific places

from a string that matches a pattern… e.g: hello %s, welcome to %s

Question 8

How to add a table look like to cmd?

Answer 8

|%7s|%7s|%7s|

Question 9

What does the log.println does? How to save the log to a file instead of cmd?

Answer 9

Print a string with the date and time on it (military format).
os.OpenFile(“asd.txt”, os.O_CREATE|os.O_APPEND|os.WRONLY, 0666) then log.SetOutput

Question 10

what does the logFatal does?

Answer 10

Log a message and closes and kills the application.

Question 11

Can I create one logger for each error level using the same file?

Answer 11

Yes. Just call log.New

Question 12

How to trace the whole execution of my app to collect metrics/profiling and other low-level information. How to read a trace file?

Answer 12

trace.Start(file here).

With the trace tool: go tool trace trace.out

Question 13

What does the time package do?

Answer 13

Get time, format time and calculate time.

Question 14

When to use the wall clock? When the wall clock useful and not useful?

Answer 14

current time of the day.
Useful for human-readable time.
Not useful to calculate time spans.

Question 15

When to use the monotonic clock?

Answer 15

• to measure time

- not subject to variation

Question 16

Why using wall clock time is not as reliable as monotonic time?

Answer 16

Because ntp can kick in and change the OS clock affecting all measurements.

Question 17

how to get the time now? Does it return wall clock or monotonic time?

Answer 17

time.Now()
Returns both (inside a struct)

Question 18

How to format the date?

Answer 18

t := time.Now()

t.Format(time.Kitchen)

Question 19

How to sleep in go? What is the unit of measure?

Answer 19

time. Sleep()

nanoseconds. .. 1000000000 = 1 second

Question 20

What function to use to know the elapsed time in go? How to get the time until something needs to happen?

Answer 20

time. Since(myDate)

time. Until(myDate)

Question 21

What does the string package do?

Answer 21

All strings manipulation.

Question 22

What is a string in go?

Answer 22

A read-only slice of bytes

Question 23

What goes do when the string is modified? Does it change the existing strings in memory? why?

Answer 23

Creates a copy and do the modifications in the new memory location.
no because it is a read-only slice of bytes.

Question 24

Are strings indexed? Where does the index start? Does it return a char?

Answer 24

Yes. 0. No, returns a byte.

Question 25

How to make the string index to return a char instead of a byte?

Answer 25

Use the array notation: 0:1

Question 26

What library compares strings? What does it return if two strings are the same?

Answer 26

strings.Compare

returns 0

Question 27

How to compare strings case insensitive?

Answer 27

strings.EqualFold

Question 28

How to replace a string in go?

Answer 28

strings.Replace(full strings, sub string, how many times to replace… -1 all of them)

Question 29

What library deals with regular expressions?

Answer 29

regexp

Question 30

What is title case? How to do that?

Answer 30

All words starts with capital letter. strings.Title(“asd”).

Question 31

What is introspection?

Answer 31

Introspection is the ability of the application to examine , introspect and modify its own structure and behavior.

Question 32

What is a basic type?

Answer 32

primitive types: bool, integer and etc.

Question 33

What is an aggregate type? Give two examples.

Answer 33

Types that are made of one or more types (including basic types) to make an object. Arrays and structs.

Question 34

What is an reference type? Give three examples.

Answer 34

Reference memory where the data is stored. Pointers, slices and channels.

Question 35

What is an interface?

Answer 35

Set of methods that can be used by concrete types (struct).

Question 36

What does an empty interface?

Answer 36

Means that a method can receive any argument.

Question 37

What happens when you change the content of a struct?

Answer 37

It creates a new copy of the struct.

Question 38

How to create a private field and a public field in a struct?

Answer 38

type Person struct {
privateName string
PublicName string
}

Question 39

When can I set a private struct field in go?

Answer 39

In its constructor.

Question 40

Which package handles reflection?

Answer 40

reflect

Question 41

How to get the name of a type? How to get all the values within a structure? How to know which kind of type is any type we want?

Answer 41

reflect.typeOf(), reflect.ValueOf(), reflect.TypeOf().Kind()

Question 42

How to create a new type on runtime?

Answer 42

make([]Employee, 3)