Golang: Package, Import

By Xah Lee. Date: . Last updated: .

Every Go program is made up of packages.

Programs start running in package named “main”, with function “main”.

package main

import "fmt"

func main() {
	fmt.Println(3 + 4) // 7
}

Import

import name → import a package named name

The name should be a string.

package main

import "fmt"
import "math"

func main() {
    fmt.Printf("%v\n", math.Sqrt(9)) // 3
}

alternative syntax:

import (name1; name2 …)

package main

import (
    "fmt"
    "math"
)

func main() {
    fmt.Printf("%v\n", math.Sqrt(9)) // 3
}

Semicolon Optional

Semicolon ; is optional when it is at end of line.

There is a command line tool , named “gofmt”, that automatically reformat your go source code to a standard format.

Exported Names, Begin with Upper Case

A name is exported if it begins with a capital letter.

When importing a package, you can refer only to its exported names. Any “unexported” names are not accessible from outside the package.

Reference

The Go Programming Language Specification - The Go Programming Language#Packages

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Golang

  1. Compile, Run
  2. Source Encoding
  3. Package, Import
  4. Comment
  5. Print
  6. String
  7. Rune
  8. String as Chars
  9. Variable
  10. Zero Value
  11. Constant
  12. If Then Else
  13. Switch/Case
  14. Loop
  15. Basic Types
  16. Array
  17. Slice
  18. Map
  19. Struct
  20. Function
  21. regexp
  22. Read File
  23. Write to File
  24. Walk Dir
  25. Check File Exist
  26. System Call
  27. Get Script Path
  28. Pointer
  29. Defer
  30. Random Number

Examples

  1. match any regexp
  2. Validate Links
  3. Generate Sitemap

Reference

  1. Go Spec