Using "go get" produces errors:

sudo go get code.google.com/p/go-tour/gotour

package bytes: unrecognized import path "bytes"
package encoding/base64: unrecognized import path "encoding/base64"
package fmt: unrecognized import path "fmt"
package image: unrecognized import path "image"
package image/png: unrecognized import path "image/png"
package runtime: unrecognized import path "runtime"
package math/rand: unrecognized import path "math/rand"
package encoding/json: unrecognized import path "encoding/json"
package flag: unrecognized import path "flag"
package go/build: unrecognized import path "go/build"
package io/ioutil: unrecognized import path "io/ioutil"
package log: unrecognized import path "log"
package net/http: unrecognized import path "net/http"
package os: unrecognized import path "os"
package os/exec: unrecognized import path "os/exec"
package path/filepath: unrecognized import path "path/filepath"
package regexp: unrecognized import path "regexp"
package strconv: unrecognized import path "strconv"
package strings: unrecognized import path "strings"
package sync: unrecognized import path "sync"

I want to play with gotour, but it can't retrieve the package. The same thing happens to packages on github. Also, my $GOROOT is set to /usr/lib/go