Fix issue #1150 (#1248)

To summarize the issue, running `swag fmt` will set (at least) 2 spaces between the attribute tag and the rest of the comment. But this is a problem for struct with single comment:

```diff
type Example struct {
	Foobar string
-} // @name Example
+} // @name  Example
```

Indeed the doc generation doesn't interpret this correctly for struct (it completely ignore it).

So there are 2 solutions:

- fix the indent (which is feel more natural)
- fix the doc generation to correctly parse 2 spaces

This commit is fixing the indent part.

Basically I just set the padding=1 on `tabwriter`.

The cons is that it will also impacts all other godocs.

For instance (taken from the readme):

```diff
-// @title           Swagger Example API
-// @Version         1.0
-// @description     This is a sample server celler server.
-// @termsofservice  http://swagger.io/terms/
+// @title          Swagger Example API
+// @Version        1.0
+// @description    This is a sample server celler server.
+// @termsofservice http://swagger.io/terms/
```

formatter.go

@@ -78,7 +78,7 @@ func formatComments(fileName string, contents []byte, formattedComments []byte,
 }
 
 func formatFuncDoc(commentList []*ast.Comment, formattedComments io.Writer, oldCommentsMap map[string]string) {
-	w := tabwriter.NewWriter(formattedComments, 0, 0, 2, ' ', 0)
+	w := tabwriter.NewWriter(formattedComments, 0, 0, 1, ' ', 0)
 
 	for _, comment := range commentList {
 		text := comment.Text

formatter_test.go

@@ -64,47 +64,47 @@ func Test_FormatMain(t *testing.T) {
 	func main() {}`
 
 	want := `package main
-	// @title           Swagger Example API
-	// @version         1.0
-	// @description     This is a sample server Petstore server.
-	// @termsOfService  http://swagger.io/terms/
+	// @title          Swagger Example API
+	// @version        1.0
+	// @description    This is a sample server Petstore server.
+	// @termsOfService http://swagger.io/terms/
 
-	// @contact.name   API Support
-	// @contact.url    http://www.swagger.io/support
-	// @contact.email  support@swagger.io
+	// @contact.name  API Support
+	// @contact.url   http://www.swagger.io/support
+	// @contact.email support@swagger.io
 
-	// @license.name  Apache 2.0
-	// @license.url   http://www.apache.org/licenses/LICENSE-2.0.html
+	// @license.name Apache 2.0
+	// @license.url  http://www.apache.org/licenses/LICENSE-2.0.html
 
-	// @host      petstore.swagger.io
-	// @BasePath  /v2
+	// @host     petstore.swagger.io
+	// @BasePath /v2
 
-	// @securityDefinitions.basic  BasicAuth
+	// @securityDefinitions.basic BasicAuth
 
-	// @securityDefinitions.apikey  ApiKeyAuth
-	// @in                          header
-	// @name                        Authorization
+	// @securityDefinitions.apikey ApiKeyAuth
+	// @in                         header
+	// @name                       Authorization
 
-	// @securitydefinitions.oauth2.application  OAuth2Application
-	// @tokenUrl                                https://example.com/oauth/token
-	// @scope.write                             Grants write access
-	// @scope.admin                             Grants read and write access to administrative information
+	// @securitydefinitions.oauth2.application OAuth2Application
+	// @tokenUrl                               https://example.com/oauth/token
+	// @scope.write                            Grants write access
+	// @scope.admin                            Grants read and write access to administrative information
 
-	// @securitydefinitions.oauth2.implicit  OAuth2Implicit
-	// @authorizationurl                     https://example.com/oauth/authorize
-	// @scope.write                          Grants write access
-	// @scope.admin                          Grants read and write access to administrative information
+	// @securitydefinitions.oauth2.implicit OAuth2Implicit
+	// @authorizationurl                    https://example.com/oauth/authorize
+	// @scope.write                         Grants write access
+	// @scope.admin                         Grants read and write access to administrative information
 
-	// @securitydefinitions.oauth2.password  OAuth2Password
-	// @tokenUrl                             https://example.com/oauth/token
-	// @scope.read                           Grants read access
-	// @scope.write                          Grants write access
-	// @scope.admin                          Grants read and write access to administrative information
+	// @securitydefinitions.oauth2.password OAuth2Password
+	// @tokenUrl                            https://example.com/oauth/token
+	// @scope.read                          Grants read access
+	// @scope.write                         Grants write access
+	// @scope.admin                         Grants read and write access to administrative information
 
-	// @securitydefinitions.oauth2.accessCode  OAuth2AccessCode
-	// @tokenUrl                               https://example.com/oauth/token
-	// @authorizationurl                       https://example.com/oauth/authorize
-	// @scope.admin                            Grants read and write access to administrative information
+	// @securitydefinitions.oauth2.accessCode OAuth2AccessCode
+	// @tokenUrl                              https://example.com/oauth/token
+	// @authorizationurl                      https://example.com/oauth/authorize
+	// @scope.admin                           Grants read and write access to administrative information
 	func main() {}`
 
 	testFormat(t, "main.go", contents, want)
@@ -132,17 +132,17 @@ func Test_FormatApi(t *testing.T) {
 
 	import "net/http"
 
-	// @Summary      Add a new pet to the store
-	// @Description  get string by ID
-	// @ID           get-string-by-int
-	// @Accept       json
-	// @Produce      json
-	// @Param        some_id  path      int           true  "Some ID"  Format(int64)
-	// @Param        some_id  body      web.Pet       true  "Some ID"
-	// @Success      200      {string}  string        "ok"
-	// @Failure      400      {object}  web.APIError  "We need ID!!"
-	// @Failure      404      {object}  web.APIError  "Can not find ID"
-	// @Router       /testapi/get-string-by-int/{some_id} [get]
+	// @Summary     Add a new pet to the store
+	// @Description get string by ID
+	// @ID          get-string-by-int
+	// @Accept      json
+	// @Produce     json
+	// @Param       some_id path     int          true "Some ID" Format(int64)
+	// @Param       some_id body     web.Pet      true "Some ID"
+	// @Success     200     {string} string       "ok"
+	// @Failure     400     {object} web.APIError "We need ID!!"
+	// @Failure     404     {object} web.APIError "Can not find ID"
+	// @Router      /testapi/get-string-by-int/{some_id} [get]
 	func GetStringByInt(w http.ResponseWriter, r *http.Request) {}`
 
 	testFormat(t, "api.go", contents, want)
@@ -156,9 +156,9 @@ func Test_NonSwagComment(t *testing.T) {
 	// @ Accept json
 	// This is not a @swag comment`
 	want := `package api
-	// @Summary      Add a new pet to the store
-	// @Description  get string by ID
-	// @ID           get-string-by-int
+	// @Summary     Add a new pet to the store
+	// @Description get string by ID
+	// @ID          get-string-by-int
 	// @ Accept json
 	// This is not a @swag comment`
 
@@ -170,7 +170,7 @@ func Test_EmptyComment(t *testing.T) {
 	// @Summary Add a new pet to the store
 	// @Description  `
 	want := `package empty
-	// @Summary  Add a new pet to the store
+	// @Summary Add a new pet to the store
 	// @Description`
 
 	testFormat(t, "empty.go", contents, want)
@@ -181,8 +181,8 @@ func Test_AlignAttribute(t *testing.T) {
 	// @Summary Add a new pet to the store
 	//  @Description Description`
 	want := `package align
-	// @Summary      Add a new pet to the store
-	// @Description  Description`
+	// @Summary     Add a new pet to the store
+	// @Description Description`
 
 	testFormat(t, "align.go", contents, want)