Go (Golang) code examples and notes.

blank_identifier

http_get

Makes a http get request using the blank identifier to ignore exceptions.

pollution

Simple code that declares a variable that is never used, its asign the var to a blank identifier to avoid declared and unused error.

by_ref_and_by_val

A program that calls two functions, one recive arguments by val and the other recive arguments by ref. It uses pointers to pass by ref.

Concurrency & Parallelism

atomicity

Provides the capability to access a var only one process at a time. This code uses an atomic function to modify a variable and avoiding simultaneous access to it.

Channels

Shows how to share values through channels between two processes.

The optional <- operator specifies the channel direction, send or receive. If no direction is given, the channel is bidirectional. A channel may be constrained only to send or only to receive by conversion or assignment.

chan T          // can be used to send and receive values of type T
chan<- float64  // can only be used to send float64s
<-chan int      // can only be used to receive ints

Source: https://golang.org/ref/spec#Channel_types

channels_and_waitgroup

How to use channels and WaitGroups in the same program.

pipeline_pattern

What is a pipeline?

There's no formal definition of a pipeline in Go; it's just one of many kinds of concurrent programs. Informally, a pipeline is a series of stages connected by channels, where each stage is a group of goroutines running the same function. In each stage, the goroutin.

• receive values from upstream via inbound channels.
• perform some function on that data, usually producing new values.
• send values downstream via outbound channels.

Each stage has any number of inbound and outbound channels, except the - first and last stages, which have only outbound or inbound channels, respectively. The first stage is sometimes called the source or producer; the last stage, the sink or consumer.

Source: https://blog.golang.org/pipelines

An example of pipeline comunication pattern.

pure_channels

How to manage multiple threads using the same channel with no other library.

concurrency

Is the composition of independently executing processes (dealing with a lot of things at once).

An example code that implements concurrency using the go keyword for creating goroutine and a WaitGroup just for keeping the main thread alive until all other threads ends.

parallelism

Is the simultaneously execution of (possibly related) computations (doing a lot of things at once).

An example code that shows how to implements parallelism using runtime.GOMAXPROCS() function inside the init() function.

rc_mutex

Example of a rance condition code and mutex for preventing unwanted behavio r.

constants

Program that declares and use some constants, it also use the iota value.

iota: a small amount of something

control_flow

Code example that implements the uses for the for statement.

• C/Java for style
• Like while statement sustitution
• Like do for infinite loops
• With the continue keyword

Convertion and Assertion

Convertion: Transform a value of certain type to another (casting or parsing in other languajes). Assertion: Treats a value of one type as if it were another, without converting it.

assertion_ex

Code that shows how to use assertion (only works with interfaces).

convertion_ex

Code example that shows how to convert a typed value to another using strconv library.

data_structures

Basic data structuresand how to deal with.

array_and_slice

Example with an Array and a Slice and the differences between these types.

slice_example

How to declare a slice and append elements to it.

maps

Example code of maps declaration and manipulation.

struct

This code shows how to create a custom type based on struct type, how to use it in a var declaration and how to change its field's values.

fmt_verbs

Uses some format verbs to display a number.

• Deciamal
• Binary
• Char
• Octal
• Hex (3 formats)

for_and_format_examples

Uses a for to generate a numerical secuences and display every generated number in three formats.

• Decimal %d
• Binary %b
• Hex %#X
• Char %q

for_and_module_op

Code example that implements a for to generate a counter and a conditional (if) to clasificate generated numbers in odd and even using a module operation x % 2.

functions

Working with functions.

anon_function

A simple code that shows how to declare and execute a anonymous function.

callback

Example of a function call that needs a callback function to do certain things.

returns

Example of three types of function's returns

• helloWorld: A simple (and traditionsl) single value return
• greet: A named var return
• names: A multiple values return

defer

Code that uses the word defer to make a function call be executed at the end of the current function.

variadic_args

Example of a function call that passes variadic arguments using the variadic technique.

variadic_params

Example of a function that can recive a unlimited number of arguments and stores in a collection, it's called variadic function.

inner_functions

Program with inner functions and functions that returns functions as result. Something like functions inception.

Interfaces

Some interfaces examples.

empty_interface

How to use empty interface to create a function that could manage any type of data/object.

simple_interface

Code that shows how to declare an interface and work with it.

sort_exercise

Requirements:

Use https://godoc.org/sort to sortthe following:

(1)
type people []string
studyGroup := people{"Zeno", "John", "Al", "Jenny"}

(2)
s := []string{"Zeno", "John", "Al", "Jenny"}

(3)
n := []int{7, 4, 8, 2, 9, 19, 12, 32, 3}

JSON

Working with JSON

json_decoder

How to convert a streammed JSON text to an object.

Note: Use this for reading JSON through the web.

json_encoder

How to convert an object to a JSON string to write it on a stream.

Note: Use this for sending Objects JSON through the web.

json_to_struct_unmarshal

Having a string with JSON content, this code will assign its values to an instance of a type that has the same exported fields using json.unmarshal() method.

struct_to_json_marshal

Having a custom class object(struct), this code will convert it to a JSON formated string using json.Marshal() method.

memmory_address

A wey to get var's memmory address, good introduction to pointers.

nested_loops

Example of nested loops, prints values of both vars.

packages_and_imports

How to use the ìmport statement for multiple libs.

pointers

How to declares and use pointers in GO.

runes

runes generator example rune = char, rune type is an alias of int32.

switch_case_default

Example code using switch statements.

switch_on_types

An example of how to implement a type based switch function.

types

A program that defines twoo custom types using struct, one inside the other; both of them has a method with the same name that the code calls for each type, it also contains a function that receive a pointer to a custom type.

variables

Example about the both ways to declare a variable.

vars_scope

How does scopes works on Go:

main

Main code, only imports a lib and calls a functions

outter

Has two files in the same package, one has the var declaration and the other has the function that prints text messages.