Overview
Installation
brew install go
Configuration
Setup default workspace
mkdir ~/go
mkdir ~/go/src
Hello World Example
vi helloworld.go
package main import ( "fmt" ) func main(){ fmt.Println("Hello World") }
Run it
go run helloworld.go
Compile it
go build
Install it
go install
Commands
| Command | Description |
|---|---|
| go run <src.go> | Run some code |
| go build | Compile the code. Outputs to local folder. Executable has folder as name. |
| go install | Compiles and places the output in workspace/bin |
| go env GOPATH | Outputs the default workspace folder |
Variables
Variables are defined using the following syntax:
var <variablename> <type>
example:
var x int
All variables have a zero value and are pre-initialized to their zero value. For example, an int would have a zero value of 0 and a string would have a zero value of empty string "".
Initializing the variable at declaration time:
var x int = 5
Quick Syntax: infers type based on value.
x:=5
Example:
package main import ( "fmt" ) func main(){ var x int x = 5 fmt.Println(x) }
If Statements
package main import ( "fmt" ) func main(){ x := 7 if x > 6 { fmt.Println("More than 6") } else if x < 2 { } else { } }
Arrays
package main import ( "fmt" ) func main(){ //fix size var a [5]int a[2] = 7 fmt.Println(a) a:= [5]int{5,4,3,2,1} fmt.Println(a) //slices a:= [] int{5,4,3,2,1} a = append(a,13) fmt.Println(a) }
Maps
package main import ( "fmt" ) func main(){ vertices := make(map[string]int) vertices["triangle"] = 2 vertices["square"] = 3 vertices["tree"] = 12 delete(vertices, "square") fmt.Println(vertices["traingle"]) fmt.Println(vertices) }
Loops
The only type of look in go is the for loop.
package main import ( "fmt" ) func main(){ //for loop for i :=0; i<5; i++{ fmt.Println(i) } //while loop j:=0 for j<5 { fmt.Println(j) j++ } //loop over array or slice arr := []string{"a"m"b","c"} for index, value := range arr { fmt.Println("index:", index, "value:", value) } //loop over a map m := make(map[string]int) m["triangle"] = 2 m["square"] = 3 for key, value := range m { fmt.Println("key:", key, "value:", value) } }
Functions
Example showing error return
package main import ( "fmt" "error" "math" ) func main() { result, err := sqrt(16) if err != nil { fmt.Println(err) } else { fmt.Println(result) } } func sqrt(x float64) (float64, error ) { if x < 0 { return 0, errors.New("Undefined for negative numbers") } return math.Sqrt(x), nil }
Structs/Types
Example of Person Type
package main import ( "fmt" ) type person struct { name string age int } func main(){ p:= person{name: "Jake", age: 23 } fmt.Println(p) fmt.Println(p.age) }
Pointers
Pass by Reference Example
package main import ( "fmt" ) func main(){ i := 7 inc(&i) fmt.Println(i) } func inc(x *int) { *x++ }
Concurrency
Go supports concurency by the use of the go command. All go functions in the background will terminate when the main terminates.
package main import ( "fmt" ) func main(){ //run in background go count("sheep") go count("fish") //wait for keyboard press before exiting fmt.Scanln() } func count(thing string) { for i:=0; true; i++ { fmt.Println(i, thing) time.Sleep(time.Millisecond * 500) } }
Using Channels
Channels are blocking
package main import ( "fmt" "time" ) func main(){ //make channel of type string c := make(chan,string) //run in background go count("sheep", c) //block until message is pushed to the channel msg:= <- c fmt.Println(msg) } func count(thing string, c chan string) { for i:=0; i <= 5; i++ { //send message on channel c <- thing time.Sleep(time.Millisecond * 500) } }
In the above code, the program exits once the count routine returns a message on the channel.
package main import ( "fmt" "time" ) func main(){ //make channel of type string c := make(chan,string) //run in background go count("sheep", c) //loop until count function closes the channel for { msg, open := <- c if !open { //channel closed, break out of for loop break } } fmt.Println(msg) } func count(thing string, c chan string) { for i:=0; i <= 5; i++ { //send message on channel c <- thing time.Sleep(time.Millisecond * 500) } //close channel close(c) }
References
| Reference | URL |
|---|---|
| Learn Go in 12 Minutes | https://www.youtube.com/watch?v=C8LgvuEBraI |
| Concurrency in Go | https://www.youtube.com/watch?v=LvgVSSpwND8 |
| Go Packages | https://golang.org/pkg/ |
| Go By Examples | https://gobyexample.com/ |