Packages in Go and Other Things

• Packages in Go are the building blocks of Go programs that divide the content into understandable parts

• you can import similar packages in this format

  import (
  
  "github.com/devopsforgo/mypackage"
  jpackage "github.com/johnsilver/mypackage"
  
  )
  
  // use it this way
  mypackage.Print()
  jpackage.Send()
  

• To import a package that you won't use mainly because the presence of the package causes something to happen, you can do it by prepending an underscore(_) before the package name like so

  package main
  
  import (
  	"fmt"
  	_ "sync"
  )
  

• The entrance point for any Go binary is a package named main that has a function called main()

• The init function runs before the main() function, this is useful in situations where you need to assign command line flags to variables before you call the main function.

• Go is a statically typed language

• In a statically typed language, the type is both what is stored in the variable and what can be stored in the variable.

• Go Built-in Types

  • bool
  • string
  • struct
  • byte (alias for uint8)
  • rune (alias for int32) - representation of a utf-8 character. done by adding a single quote before a value
  • float32 float64
  • int int8 int16 int32 int64
  • uint uint8 uint16 uint32 uint64
  • uintptr - holds a pointer address
  • complex64 complex128 - complex numbers

• package level → meaning outside a function

• you can only declare a variable like this within a function

  hello := "this is a test"
  

• The important thing to remember when using := is that it means create and assign. If the variable already exists, you cannot use :=, but you must use =, which does only an assignment.

• A scope is the part of a program in which a variable can be seen.

• Go has the following variable scope:

  • Package scope → declared outside a function
  • Function scope → declared in a function
  • Statement scope → declared in a statement within a function (for loop, if/else)

Best practices for packaging your Go Code

• make your struct and interfaces in uppercase so that you can access them directly
• The idea is to make sure to have less code in the main.go function
• use a pointer when making a change to a variable in a struct and want to persist the change