fix golint issues in rest (#529)

rest/internal/context/params.go

@@ -7,6 +7,7 @@ import (
 
 var pathVars = contextKey("pathVars")
 
+// Vars parses path variables and returns a map.
 func Vars(r *http.Request) map[string]string {
 	vars, ok := r.Context().Value(pathVars).(map[string]string)
 	if ok {
@@ -16,6 +17,7 @@ func Vars(r *http.Request) map[string]string {
 	return nil
 }
 
+// WithPathVars writes params into given r and returns a new http.Request.
 func WithPathVars(r *http.Request, params map[string]string) *http.Request {
 	return r.WithContext(context.WithValue(r.Context(), pathVars, params))
 }