enforce the use of goimports (#248)

* enforce the use of goimports

Instead of enforcing `gofmt`, enforce `goimports`, which also asserts
a separate section for non-builtin packages.

* run `goimports` everywhere

* exclude generated .pb.go files

cmd/nebula-cert/main_test.go

@@ -3,10 +3,11 @@ package main
 import (
 	"bytes"
 	"errors"
-	"github.com/stretchr/testify/assert"
 	"io"
 	"os"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 //TODO: all flag parsing continueOnError will print to stderr on its own currently

cmd/nebula-cert/print.go

@@ -4,11 +4,12 @@ import (
 	"encoding/json"
 	"flag"
 	"fmt"
-	"github.com/slackhq/nebula/cert"
 	"io"
 	"io/ioutil"
 	"os"
 	"strings"
+
+	"github.com/slackhq/nebula/cert"
 )
 
 type printFlags struct {

cmd/nebula-cert/print_test.go

@@ -2,12 +2,13 @@ package main
 
 import (
 	"bytes"
-	"github.com/slackhq/nebula/cert"
-	"github.com/stretchr/testify/assert"
 	"io/ioutil"
 	"os"
 	"testing"
 	"time"
+
+	"github.com/slackhq/nebula/cert"
+	"github.com/stretchr/testify/assert"
 )
 
 func Test_printSummary(t *testing.T) {

cmd/nebula-cert/verify.go

@@ -3,12 +3,13 @@ package main
 import (
 	"flag"
 	"fmt"
-	"github.com/slackhq/nebula/cert"
 	"io"
 	"io/ioutil"
 	"os"
 	"strings"
 	"time"
+
+	"github.com/slackhq/nebula/cert"
 )
 
 type verifyFlags struct {

cmd/nebula-cert/verify_test.go

@@ -3,13 +3,14 @@ package main
 import (
 	"bytes"
 	"crypto/rand"
-	"github.com/slackhq/nebula/cert"
-	"github.com/stretchr/testify/assert"
-	"golang.org/x/crypto/ed25519"
 	"io/ioutil"
 	"os"
 	"testing"
 	"time"
+
+	"github.com/slackhq/nebula/cert"
+	"github.com/stretchr/testify/assert"
+	"golang.org/x/crypto/ed25519"
 )
 
 func Test_verifySummary(t *testing.T) {

cmd/nebula-service/main.go

@@ -3,9 +3,10 @@ package main
 import (
 	"flag"
 	"fmt"
+	"os"
+
 	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula"
-	"os"
 )
 
 // A version string that can be set with

cmd/nebula-service/service.go

@@ -2,12 +2,12 @@ package main
 
 import (
 	"fmt"
-	"github.com/sirupsen/logrus"
 	"log"
 	"os"
 	"path/filepath"
 
 	"github.com/kardianos/service"
+	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula"
 )
 

cmd/nebula/main.go

@@ -3,9 +3,9 @@ package main
 import (
 	"flag"
 	"fmt"
-	"github.com/sirupsen/logrus"
 	"os"
 
+	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula"
 )