Go Keyword import

External

• https://golang.org/ref/spec#Import_declarations

Internal

• Lexical Structure
• Packages

Overview

An import declaration states that the current package depends on the functionality of the imported package and wants access to its name space. Thus, the current package gains access to the exported identifiers exposed by the imported package.

...
import [package-name-alias] "package-path-string-literal"
...

Example

...
import "net/http"
import "project1/blue"
...

The package path is enclosed in double quotes. It is a string literal. It is NOT the package name, but it helps the compiler to locate the package.

It represents a local file system path fragment. That path fragment lives under a src directory whose parent is listed in GOPATH. For more details on how GOPATH works go to GOPATH.

Note that if the path has multiple segments, only the last one can used to prefix identifiers in the program. For example, if we import import "project1/blue", we can use only blue to qualify identifiers from that package: blue.DoSomethingBlue()

The package-name-alias is optional, and it should be used when we have a package name conflict - we're trying to use two package whose terminal path segment is the same. If package-name-alias is not specified, the package will be referred as the last segment of the path.

The package name - the string literal that is mentioned after the package keyword when the package elements are defined and after the import keyword when the package elements are imported into another package - is a filesystem path fragment that consists in path elements separated by slashes. In the simplest case, the path fragment contains just one element. The filesystem path fragments represent directories on the local filesystem that live under "src" directories, which in turn live under parent directories that are listed in GOPATH.

Importing Multiple Packages

import (
    "fmt"
    "strings"
)

Accessing an Identifier from an Imported Package

Once a package has been declared as "imported", all exported identifiers from the imported package are available in the importing package. In order to access an individual exported identifier, the identifier should be prefixed with the name of the package. For example, in order to access the struct Box exposed by package "pkgA", we do this:

import "pkgA"
...
func f() {
    ...
    var b pkgA.Box
    ...
}

How Packages are Resolved

The algorithm is described here:

GOPATH