package code.google.com/p/go.example/hello: exec: "hg": executable file not found in %PATH%. How to get remote golang packages?

I do as written an the Golang tutorial http://golang.org/doc/code.html#remote

My env settings:

C:\sbox\go\example>set go
    GOPATH=C:\sbox\go\example
    GOROOT=C:\Go

The example/ folder has only src/ folder:

C:\sbox\go\example\
             |
             --src\

Now I call go get as described and get an error:

C:\sbox\go\example>go get code.google.com/p/go.example/hello
# cd .; hg clone -U https://code.google.com/p/go.example C:\sbox\go\example\src\code.google.com\p\go.example
package code.google.com/p/go.example/hello: exec: "hg": executable file not found in %PATH%

After calling go get, though, my example/ folder becomes like this:

C:\sbox\go\example\
             |
             --src\
                |
                code.google.com\
                       |
                       --p\

And that's all. Nothing more installed.

Then I add a code to my directory structure and it becomes like this:

C:\sbox\go\example\
             |
             --src\
                |
                ---code.google.com\
                |        |
                |        --p\
                |
                ---github.com\
                       |
                       --user\
                           |
                           --hello\
                           |   |
                           |   --hello.go
                           |
                           --newmath\
                                |
                                --sqrt.go

hello.go is like this:

package main

import (
	"fmt"
	"github.com/user/newmath"
	//"code.google.com/p/go.example/newmath"
)

func main() {
	fmt.Printf("Hello, world.  Sqrt(2) = %v\n", newmath.Sqrt(2))
}

sqrt.go is like this:

// Package newmath is a trivial example package.
package newmath

// Sqrt returns an approximation to the square root of x.
func Sqrt(x float64) float64 {
	z := 0.0
	for i := 0; i < 1000; i++ {
		z -= (z*z - x) / (2 * x)
	}
	return z
}

I just cope/paste them. All as written in the tutorial. Then I do go install and run the project. All works fine:

C:\sbox\go\example\src\github.com\user\hello>go install
    
C:\sbox\go\example\bin>hello
Hello, world.  Sqrt(2) = 1.414213562373095

Now I again run go get and get the same error:

C:\sbox\go\example>go get code.google.com/p/go.example/hello
# cd .; hg clone -U https://code.google.com/p/go.example C:\sbox\go\example\src\code.google.com\p\go.example
package code.google.com/p/go.example/hello: exec: "hg": executable file not found in %PATH%

Ok, I add bin/ directory to the PATH and run go get again but get the same error:

C:\sbox\go\example>set PATH=%PATH%;C:\sbox\go\example\bin

C:\sbox\go\example>go get code.google.com/p/go.example/hello
# cd .; hg clone -U https://code.google.com/p/go.example C:\sbox\go\example\src\code.google.com\p\go.example
package code.google.com/p/go.example/hello: exec: "hg": executable file not found in %PATH%

What do I need to do get the result as described in the tutorial - remote packages are installed and I can use them?

The package you are trying to install is under the Mercurial (hg) source control system. You need to install Mercurial to be able to clone the package.