Go Lunch 'n Learn example code
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01-hello.go
02-if.go
03-switch.go
04-structs.go
05-slices.go
06-maps.go
07-closures.go
08-methods.go
09-interfaces.go
10-goroutine.go
11-channels.go
12-channels-more.go
13-range.go
14-select.go
README.md

README.md

Go Go?

Go Lunch 'n Learn example code. Most of the code is taken from http://tour.golang.org.

Anything that is not covered in this lunch 'n learn can likely be found here: http://golang.org/doc/effective_go.html

Interesting Aspects

  • Go is built has a concurrent, garbage-collected language with fast compilation. Large applications should compile in a few seconds on a single machine.
  • When compiling, unused variables and imports are considered errors and stop compilation.
  • Go does not have exceptions because the designers believe them to be cumbersome. Instead Go has Defer, Panic, and Recover.

Hello World

Packages

  • All Go programs are made up of packages
  • Programs start running in package main
  • import is used to import other packages

Exported Names

  • After importing you can refer to the name a package exports
  • Go exports anything that begins with a capital letter

Variables

  • Declare with either var or := (:= can only be used inside functions)
  • Type is declared after variable name
  • If initializer is present, type can be ommitted
  • := uses implicity typing
  • Constants can be a character, string, boolean, or a numeric value

Functions

  • Return value type always comes after parameter list
  • When consecutive parameters share a type it can be shortened
  • Functions can return any number of results
  • Go functions can return result parameters that act as normal variables while inside the function and return their current value on return

Loops and Conditions

If Statements

  • No ( ) and { } are required
  • Can start with short statement before the execution of condition
  • Variables declared in the statement are only in scope until the end of the if block

For loop

  • Go only has a for loop
  • As with C, the pre and post statements can be empty and then no ; are required
  • For an infinite loop the keyword for can just be used

Switch Statements

  • Evaluates from top to bottom
  • Automatically breaks unless a case ends with a fallthrough statement
  • Switch statement without condition can be used for long if-then-else chains

Data Structures

Pointers

  • No pointer arithmetic

Structs

  • A collection of fields
  • Uses the dot accessor
  • new(T) function allocates a zeroed struct and returns a pointer to it

Slices

  • Points to an array of values
  • len(s) is used to get the length of a slice
  • Can be re-sliced, creating a new slice value that points to the same array
    • expression: s[lo:lo]
    • evaluates from lo through hi-1, inclusive
    • s[lo:lo] is empty and s[lo:lo+1] has one element
  • Slices are created with the make() function
  • cap(s) is used to get the capacity of a slice

Maps

  • Key value pair structure
  • Can be created with make()
  • delete() is used to remove an object from a map
  • A loopup returns two parameters, the value (if any) and a boolean indicating if the element exists in the map

Closures

  • Work just like closures in JavaScript

Methods and Interfaces

Methods

  • Go does not have classes
  • Methods can be attached to structs
  • The method receiver appears between func and the method name
  • The method receiver should be a pointer to the type, this allows the method to modify properties of the type

Interfaces

  • Interface type is defined as a set of methods
  • A value of interface type can hold any value that implements those methods
  • Allows for increased decoupling

Concurrent Programming

Goroutines

  • Lightweight thread, managed by Go runtime
  • go is the keyword used to start a new goroutine

Channels

  • Typed conduit through which you can send and receive values with the channel operator, <-
  • Must be created before use
  • By default, sends and receives block until the other side is ready. This allows goroutines to synchronize without explicit locks or condition variables
  • Can be buffered, provide buffer amount as the second argument to make
  • Sends to a buffered channel block only when the buffer is full. Receives block when the buffer is empty.

Range and Close

  • A sender can close a channel to indicate that no more values with be sent
  • A receiver can check if a channel is open by utilizing the second return value
  • A range loop can be used to receive values until the channel is closed

Select blocks

  • A select block blocks until one of its cases can run, then it executes that case. It chooses one at random if multiple are ready.
  • default can be used to create a non-blocking pattern