uri_test.go: test filename with $GOROOT

uri_test.go

@@ -5,12 +5,15 @@
 package uri
 
 import (
+	"os"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
 )
 
 func TestFile(t *testing.T) {
+	os.Setenv("GOROOT", "/go/root")
+
 	tests := []struct {
 		name    string
 		path    string
@@ -23,6 +26,12 @@ func TestFile(t *testing.T) {
 			want:    URI(FileScheme + hierPart + "/users/me/c%23-projects"),
 			wantErr: false,
 		},
+		{
+			name:    "Goroot",
+			path:    "$GOROOT/bin/go",
+			want:    URI(FileScheme + hierPart + "/go/root/bin/go"),
+			wantErr: false,
+		},
 		{
 			name:    "Invalid",
 			path:    "users-me-c#-projects",