docs: start golang cheatsheet

languages/golang.md

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+# Golang
+
+## Summary
+
+- Introduction
+    - [Hello World](#hello-world)
+    - [Go CLI Commands](#go-cli-commands)
+    - [Go Modules](#go-modules)
+- Syntax
+    - [Basic Types](#basic-types)
+    - [Variables](#variables)
+
+## Hello World
+
+```go
+package main 
+
+import "fmt"
+
+func main() {
+    fmt.Println("Hello World!")
+}
+```
+
+## Go CLI Commands
+
+```bash
+# Compile & Run code
+$ go run [file.go]
+
+# Compile
+$ go build [file.go]
+# Running compiled file
+$ ./hello 
+
+# Test packages
+$ go test [folder]
+
+# Install packages/modules
+$ go install [package]
+
+# List installed packages/modules
+$ go list
+
+# Update packages/modules
+$ go fix
+
+# Format package sources
+$ go fmt
+
+# See package documentation
+$ go doc [package]
+
+# Add dependencies and install
+$ go get [module]
+
+# See Go environment variables
+$ go env
+
+# See version
+$ go version
+```
+
+## Go Modules
+
+- Go projects are called **modules**
+- Each module has multiple **packages**
+- Each package should has a scoped functionality. Packages talk to each other to compose the code
+- A module needs at least one package, the **main**
+- The package main needs a entry function called **main**
+
+```bash
+# Create Module
+$ go mod init [name] 
+```
+Tip: By convention, modules names has the follow structure:
+
+domain.com/user/module/package
+
+Example: github.com/spf13/cobra
+
+## Basic Types
+
+|   Type    |   Set of Values   |   Values  |
+|:---------:|:-----------------:|:---------:|
+| bool | boolean | true/false |
+| string | array of characters | needs to be inside "" |
+| int | integers | 32 or 64 bit integer |
+| int8 | 8-bit integers | [ -128, 128 ] |
+| int16 | 16-bit integers | [ -32768, 32767] |
+| int32 | 32-bit integers | [ -2147483648, 2147483647] |
+| int64 | 64-bit integers | [ -9223372036854775808, 9223372036854775807 ] |
+| uint8 | 8-bit unsigned integers | [ 0, 255 ] |
+| uint16 | 16-bit unsigned integers | [ 0, 65535 ] |
+| uint32 | 32-bit unsigned integers | [ 0, 4294967295 ] |
+| uint64 | 64-bit unsigned integers | [ 0, 18446744073709551615 ] |
+| float32 | 32-bit float |  |
+| float64 | 64-bit float |  |
+| complex64 | 32-bit float with real and imaginary parts |  |
+| complex128 | 64-bit float with real and imaginary parts |  |
+| byte | sets of bits | alias for uint8  |
+| rune | Unicode characters | alias for int32 |
+
+## Variables
+
+```go
+// Declaration
+var int value 
+
+// Initialization
+value = 10
+
+// Declaration + Initialization + Type inference
+var isActive = true
+
+// Short declaration (only inside functions)
+text := "Hello"
+
+// Multi declaration
+var i, j, k = 1, 2, 3
+
+// Variable not initialized = Zero values
+// Numeric: 0
+// Boolean: false
+// String: ""
+
+var number int // 0
+var text string // false
+var boolean bool // ""
+
+// Type conversions
+// T(v) converts v to type T
+
+i := 1.234 // float
+int(i) // 1
+```