If you are thinking of starting to write on Go, this is what you should know.

Who is this article for?

• Go is very often used to write backend services and very rarely for everything else. There are two more popular pairs for the same: Java / C # and Python / Ruby. Go, in my opinion, is aimed precisely at taking a share from the Python / Ruby pair.
• Go inherits its strange behavior precisely from the nuances of C syntax that are unobviously hidden in the language. Since there are clear points of rejection in Go to such an extent that sometimes you want to remove the Go compiler and forget, understanding C principles and the fact that Go is in a sense a superset of C allows them to be significantly smoothed out.

What will not be in the article

• We will not say that Go is bad, because it does not have feature X, as in the language Y. Each language has its own rules of the game, its own approaches and its fans. Although I am deceiving whom, of course we will have to talk about this.
• We will not compare directly interpreted and compiled languages.

Beginning of work

Odd compiler

package main

func main()  //  
{

}

a := []string{
	"q"  //  ,  
}

package main

func main() {
	a := []string{
		"q",
	}
	//  ,   
}

for _, value := range x {
    total += value
}

«»

« , (..: ) . , , , , Java, C/C++, Python. , , . .»

: Go .

var x map[string]int
x["key"] = 10

panic: runtime error: assignment to entry in nil map

tyderh , :
, , , . , .

  var i32 int32 = 0
  var i64 int64 = 0
  
  if i64 == i32 {
    
  }

package main

import (
	"fmt"
)

func eq(val1 interface{}, val2 interface{}) bool {
	return val1 == val2
}

func main() {
	var i32 int32 = 0
	var i64 int64 = 0
	var in int = 0

	fmt.Println(eq(i32, i64))
	fmt.Println(eq(i32, in))
	fmt.Println(eq(in, i64))
}

func returnsError(t bool) error {
	var p *MyError = nil
	if t {
		p = ErrBad
	}
	return p // Will always return a non-nil error.
}
err := returnsError(false)
if err != nil {
  # 
}

package main

import "fmt"

type storage struct {
	name string
}

var m map[string]storage

func main() {
	m = make(map[string]storage)
	m["pen"] = storage{name: "pen"}

	if data, ok := m["pen"]; ok {
		data.name = "-deleted-"
	}

	fmt.Println(m["pen"].name) // Output: pen
}

package main

import "fmt"

type storage struct {
	name string
}

var m map[string]*storage

func main() {
	m = make(map[string]*storage)
	m["pen"] = &storage{name: "pen"}

	if data, ok := m["pen"]; ok {
		data.name = "-deleted-"
	}

	fmt.Println(m["pen"].name) // Output: -deleted-
}

m = make(map[string]storage)

m = make(map[string]*storage)

package main

import "fmt"

var globState string = "initial"

func getState() (string, bool) {
	return "working", true
}

func ini() {
	globState, ok := getState()
	if !ok {
		fmt.Println(globState)
	}
}

func main() {
	ini()
	fmt.Println("Current state: ", globState)
}

«»

make([]int, 50, 100)
new([100]int)[0:50]

var i int = 3
j := 6

«»

result, err := function()
if err != nil {
    // ...
}

«»

if _, ok := elements["Un"]; ok {
}

db.Table("users").Select("users.name, emails.email").Joins("left join emails on emails.user_id = users.id").Scan(&results)

query := models.DB.LeftJoin("roles", "roles.id=user_roles.role_id").
  LeftJoin("users u", "u.id=user_roles.user_id").
  Where(`roles.name like ?`, name).Paginate(page, perpage)

a.GET("/users/{name}", func (c buffalo.Context) error {
  return c.Render(200, r.String(c.Param("name")))
})

elements := map[string]map[string]string{
		"H": map[string]string{
			"name":  "Hydrogen",
			"state": "gas",
		},
        }

elements := map[string](map[string]string){
        }

if result != 1 {
    t.Fatalf("result is not %v", 1)
    }

assert.NotEqual(t, result, 1, "invalid result")

string([]byte{'a'})

y.(io.Reader)

vgo mod -vendor

• — , .
• — go build . autotools/Makefile. , . — , .
• — , . , - .
• — — 1 . 1 , 1 .
• — .
• — , IDE . Go, .
• — Go , , . , Ruby .
• . :
  

  package main
  
  import (
      "fmt"
      "os"
      "log"
  )
  
  func main() {
      file, err := os.Open("file.txt")
      if err != nil {
          log.Fatal(err)
      }
      defer file.Close()
  
    b, err := ioutil.ReadAll(file)
    fmt.Print(b)
  }
  

  defer file.Close()

  , , , . ( with).

• Go , . .
• Go . - : « 5, 3». , — , 4. , .
• . . . . .
• STL , . , map array. .

• github.com/vizor-games/golang-unittest — assert check , , . , .
• godoc.org/github.com/powerman/check — , : Equal, Less,…. powerman.
• github.com/stretchr/testify — . esata.
• github.com/onsi/ginkgo — . tyderh.
• github.com/smartystreets/goconvey — BDD , , . negasus.

• Go. on-line .
• Go (en). .
• : Go 2
• : Go. Go.
• : sync.Map Go 1.9
  .