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. Print String
  8. String Backslash Escape
  9. Rune
  10. Variable
  11. Zero Value
  12. Constant
  13. If Then Else
  14. Switch/Case
  15. Loop
  16. Basic Types
  17. Array
  18. Slice
  19. Map
  20. Struct
  21. Function
  22. Closure
  23. Pointer
  24. String, Byte Slice, Rune Slice
  25. regexp
  26. Read File
  27. Write to File
  28. Walk Dir
  29. Check File Exist
  30. System Call
  31. Get Script Path
  32. Defer
  33. Random Number

Examples

  1. Match Any Regexp
  2. Find Replace
  3. Validate Links
  4. Generate Sitemap

Reference

  1. Go Spec