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