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docs: start libs section of go cheatsheet
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LuanSilveiraSouza
parent
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9349857693
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@ -2,22 +2,27 @@
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## Summary
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## Summary
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- Introduction
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- Introduction
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- [Hello World](#hello-world)
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- [Hello World](#hello-world)
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- [Go CLI Commands](#go-cli-commands)
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- [Go CLI Commands](#go-cli-commands)
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- [Go Modules](#go-modules)
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- [Go Modules](#go-modules)
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- Basic
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- Basic
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- [Basic Types](#basic-types)
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- [Basic Types](#basic-types)
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- [Variables](#variables)
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- [Variables](#variables)
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- [Operators](#operators)
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- [Operators](#operators)
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- [Conditional Statements](#conditional-statements)
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- [Conditional Statements](#conditional-statements)
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- [Loops](#loops)
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- [Loops](#loops)
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- [Arrays](#arrays)
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- [Arrays](#arrays)
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- [Functions](#functions)
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- [Functions](#functions)
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- Advanced
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- Advanced
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- [Structs](#structs)
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- [Structs](#structs)
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- [Maps](#maps)
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- [Maps](#maps)
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- [Pointers](#pointers)
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- [Pointers](#pointers)
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- [Methods and Interfaces](#methods-and-interfaces)
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- [Errors](#errors)
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- [Testing](#testing)
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- Standard Libs
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- [Package fmt](#package-fmt)
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## Hello World
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## Hello World
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@ -27,7 +32,7 @@ package main
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import "fmt"
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import "fmt"
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func main() {
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func main() {
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fmt.Println("Hello World!")
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fmt.Println("Hello Gophers!")
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}
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}
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```
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```
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@ -80,16 +85,17 @@ $ go version
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## Go Modules
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## Go Modules
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- Go projects are called **modules**
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- Go projects are called **modules**
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- Each module has multiple **packages**
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- Each module has multiple **packages**
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- Each package should has a scoped functionality. Packages talk to each other to compose the code
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- Each package should has a scoped functionality. Packages talk to each other to compose the code
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- A module needs at least one package, the **main**
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- A module needs at least one package, the **main**
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- The package main needs a entry function called **main**
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- The package main needs a entry function called **main**
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```bash
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```bash
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# Create Module
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# Create Module
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$ go mod init [name]
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$ go mod init [name]
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```
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```
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Tip: By convention, modules names has the follow structure:
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Tip: By convention, modules names has the follow structure:
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domain.com/user/module/package
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domain.com/user/module/package
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@ -102,25 +108,25 @@ Example: github.com/spf13/cobra
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## Basic Types
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## Basic Types
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| Type | Set of Values | Values |
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| Type | Set of Values | Values |
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|:---------:|:-----------------:|:---------:|
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| :--------: | :----------------------------------------: | :-------------------------------------------: |
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| bool | boolean | true/false |
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| bool | boolean | true/false |
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| string | array of characters | needs to be inside "" |
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| string | array of characters | needs to be inside "" |
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| int | integers | 32 or 64 bit integer |
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| int | integers | 32 or 64 bit integer |
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| int8 | 8-bit integers | [ -128, 128 ] |
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| int8 | 8-bit integers | [ -128, 128 ] |
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| int16 | 16-bit integers | [ -32768, 32767] |
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| int16 | 16-bit integers | [ -32768, 32767] |
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| int32 | 32-bit integers | [ -2147483648, 2147483647] |
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| int32 | 32-bit integers | [ -2147483648, 2147483647] |
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| int64 | 64-bit integers | [ -9223372036854775808, 9223372036854775807 ] |
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| int64 | 64-bit integers | [ -9223372036854775808, 9223372036854775807 ] |
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| uint8 | 8-bit unsigned integers | [ 0, 255 ] |
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| uint8 | 8-bit unsigned integers | [ 0, 255 ] |
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| uint16 | 16-bit unsigned integers | [ 0, 65535 ] |
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| uint16 | 16-bit unsigned integers | [ 0, 65535 ] |
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| uint32 | 32-bit unsigned integers | [ 0, 4294967295 ] |
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| uint32 | 32-bit unsigned integers | [ 0, 4294967295 ] |
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| uint64 | 64-bit unsigned integers | [ 0, 18446744073709551615 ] |
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| uint64 | 64-bit unsigned integers | [ 0, 18446744073709551615 ] |
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| float32 | 32-bit float | |
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| float32 | 32-bit float | |
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| float64 | 64-bit float | |
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| float64 | 64-bit float | |
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| complex64 | 32-bit float with real and imaginary parts | |
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| complex64 | 32-bit float with real and imaginary parts | |
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| complex128 | 64-bit float with real and imaginary parts | |
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| complex128 | 64-bit float with real and imaginary parts | |
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| byte | sets of bits | alias for uint8 |
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| byte | sets of bits | alias for uint8 |
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| rune | Unicode characters | alias for int32 |
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| rune | Unicode characters | alias for int32 |
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[Return to Summary](#summary)
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[Return to Summary](#summary)
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@ -171,7 +177,7 @@ const pi = 3.1415
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[Return to Summary](#summary)
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[Return to Summary](#summary)
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Arithmetic Operators
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Arithmetic Operators
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| Symbol | Operation | Valid Types |
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| Symbol | Operation | Valid Types |
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|:---------:|:-------------:|:-------------:|
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|:---------:|:-------------:|:-------------:|
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| `+` | Sum | integers, floats, complex values, strings |
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| `+` | Sum | integers, floats, complex values, strings |
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| `-` | Difference | integers, floats, complex values |
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| `-` | Difference | integers, floats, complex values |
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@ -186,7 +192,7 @@ Arithmetic Operators
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| `>>` | Right shift | integer >> unsigned integer |
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| `>>` | Right shift | integer >> unsigned integer |
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Comparison Operators
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Comparison Operators
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| Symbol | Operation |
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| Symbol | Operation |
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|:---------:|:-------------:|
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|:---------:|:-------------:|
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| `==` | Equal |
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| `==` | Equal |
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| `!=` | Not equal |
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| `!=` | Not equal |
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@ -196,7 +202,7 @@ Comparison Operators
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| `>=` | Greater or equal |
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| `>=` | Greater or equal |
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Logical Operators
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Logical Operators
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| Symbol | Operation |
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| Symbol | Operation |
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|:---------:|:-------------:|
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|:---------:|:-------------:|
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| `&&` | Conditional AND |
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| `&&` | Conditional AND |
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| `||` | Conditional OR |
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| `||` | Conditional OR |
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@ -362,6 +368,7 @@ for _, value := range slice {
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<hr/>
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<hr/>
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## Functions
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## Functions
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```go
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```go
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// Functions acts as a scoped block of code
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// Functions acts as a scoped block of code
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func sayHello() {
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func sayHello() {
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@ -540,3 +547,115 @@ Obs: Unlike C, Go doesn't have pointer arithmetics.
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[Return to Summary](#summary)
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[Return to Summary](#summary)
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<hr/>
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<hr/>
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## Methods and Interfaces
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Go doesn't have classes. But you can implement methods, interfaces and almost everything contained in OOP, but in what gophers call "Go Way"
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```go
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type Dog struct {
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Name string
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}
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func (dog *Dog) bark() string {
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return dog.Name + " is barking!"
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}
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dog := Dog{"Rex"}
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dog.bark() // Rex is barking!
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```
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Interfaces are implicitly implemented. You don't need to inform that your struct are correctly implementing a interface if it already has all methods with the same name of the interface.
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All structs implement the `interface{}` interface. This empty interface means the same as `any`.
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```go
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// Car implements Vehicle interface
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type Vehicle interface {
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Accelerate()
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}
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type Car struct {
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}
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func (car *Car) Accelerate() {
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return "Car is moving on ground"
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}
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```
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[Return to Summary](#summary)
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<hr/>
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## Errors
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Go doesn't support `throw`, `try`, `catch` and other common error handling structures. Here, we use `error` package to build possible errors as a returning parameter in functions
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```go
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import "errors"
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// Function that contain a logic that can cause a possible exception flow
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func firstLetter(text string) (string, error) {
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if len(text) < 1 {
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return nil, errors.New("Parameter text is empty")
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}
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return string(text[0]), nil
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}
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a, errorA := firstLetter("Wow")
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a // "W"
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errorA // nil
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b, errorB := firstLetter("")
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b // nil
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errorB // Error("Parameter text is empty")
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```
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[Return to Summary](#summary)
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<hr/>
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## Testing
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Go has a built-in library to unit testing. In a separate file you insert tests for functionalities of a file and run `go test package` to run all tests of the actual package or `go test path` to run a specific test file.
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```go
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// main.go
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func Sum(x, y int) int {
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return x + y
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}
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// main_test.go
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import (
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"testing"
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"reflect"
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)
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func TestSum(t *testing.T) {
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x, y := 2, 4
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expected := 2 + 4
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if !reflect.DeepEqual(sum(x, y), expected) {
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t.Fatalf("Function Sum not working as expected")
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}
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}
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```
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[Return to Summary](#summary)
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<hr/>
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## Package `fmt`
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```go
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import "fmt"
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fmt.Print("Hello World") // Print in console
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fmt.Println("Hello World") // Print and add a new line in end
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fmt.Printf("%s is %d years old", "John", 32) // Print with formatting
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fmt.Errorf("User %d not found", 123) // Print a formatted error
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```
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[Return to Summary](#summary)
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<hr/>
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