Table of Contents |
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Overview
Installation
brew install go
Add it to your Path
Add the following to your .bashrc or zshrc file
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export PATH="$PATH:$(go env GOPATH)/bin" |
Configuration
Setup default workspace
...
go build
Install it
go install
Creating a Module
Create a go.mod file
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module mymodule
go 1.18
|
Add Libraries
go get github.com/qopher/go-torrentapi
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 |
...
Code Block |
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package main
import (
"fmt"
)
func main(){
var x int
x = 5
fmt.Println(x)
} |
If Statements
Code Block |
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package main import ( "fmt" ) func main(){ x := 7 if x > 6 { fmt.Println("More than 6") } else if x < 2 { } else { } } |
Arrays
Code Block |
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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
Code Block |
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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.
Code Block |
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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
Code Block |
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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
} |
Method Set
Code Block |
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func (h handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
...
}
func (s *GracefulServer) BlockingClose() bool {
...
} |
This is called the 'receiver'. In the first case (h handler)
it is a value type, in the second (s *GracefulServer)
it is a pointer. The way this works in Go may vary a bit from some other languages. The receiving type however, works more or less like a class in most object-oriented programming. It is the thing you call the method from, much like if I put some method A
in side some class Person
then I would need an instance of type Person
in order to call A
(assuming it's an instance method and not static!).
One gotcha here is that the receiver gets pushed onto the call stack like other arguments so if the receiver is a value type, like in the case of handler
then you will be working on a copy of the thing you called the method from meaning something like h.Name = "Evan"
would not persist after you return to the calling scope. For this reason anything that expects to change the state of the receiver, needs to use a pointer or return the modified value (gives more of an immutable type paradigm if you're looking for that).
Here's the relevant section from the spec; https://golang.org/ref/spec#Method_sets
Structs/Types
Example of Person Type
Code Block |
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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
Code Block |
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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.
Code Block |
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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
Code Block |
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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.
Code Block |
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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)
} |
Organizing your Code
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/ |