You can import packages with:

import "path/to/package1"
import "path/to/package2"

or group multiple imports together:

import (
    "path/to/package1"
    "path/to/package2"
)

This will look in the corresponding import paths inside of the $GOPATH for .go files and lets you access exported names through packagename.AnyExportedName.

You can also access local packages inside of the current folder by prefacing packages with ./. In a project with a structure like this:

project
├── src
│   ├── package1
│   │   └── file1.go
│   └── package2
│       └── file2.go
└── main.go

You could call this in main.go in order to import the code in file1.go and file2.go:

import (
    "./src/package1"
    "./src/package2"
)

Since package-names can collide in different libraries you may want to alias one package to a new name. You can do this by prefixing your import-statement with the name you want to use.

import (
    "fmt" //fmt from the standardlibrary
    tfmt "some/thirdparty/fmt" //fmt from some other library
)

This allows you to access the former fmt package using fmt.* and the latter fmt package using tfmt.*.

It is considered a bad style but you can import the package into the global namespace to avoid using package prefix:

import (
    . "fmt"
)

With the above Printf is the same as fmt.Printf.

Go compiler reports an error if you import a package but don't use it. To work-around this, you can set the alias to the underscore:

import (
    _ "fmt"
)

This might be necessary if you don't use the package directly but need the side-effects of running package's init function.