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)
}
}
FunctionsÂ
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)
}
}
References
| Reference | URL |
|---|---|
| Learn Go in 12 Minutes | https://www.youtube.com/watch?v=C8LgvuEBraI |
| Go Packages | https://golang.org/pkg/ |
| Go By Examples | https://gobyexample.com/ |